ProFTPD upload fails (empty files), signal 15 in log

[martinnaj]

What I Did

Please describe what you did, including the clients you used, what errors
or messages you saw, etc.

ProFTPD killed (signal 15)
ProFTPD 1.3.7c standalone mode SHUTDOWN
ProFTPD 1.3.7c (maint) (built Fri Dec 3 2021 13:35:22 UTC) standalone mode STARTUP

When uploading a file using WebStorm FTP or FileZilla, it says 100% uploaded, however it seems any data is not written to the file. Proftpd has permissions for the directory and nothing has been changed. This started happening randomly, where restarting ProFTPD fixed the issue, it now doesn't fix the issue and files fail to upload. Somehow I was able to upload a file once, however since then all attempt have failed. The file is created when an upload is attempted however contains 0 bytes of data.

Filezilla log:

Status:	Resolving address of xx-xx.co.uk
Status:	Connecting xx.xx.xx.xx:21...
Status:	Connection established, waiting for welcome message...
Status:	Insecure server, it does not support FTP over TLS.
Status:	Server does not support non-ASCII characters.
Status:	Logged in
Status:	Starting upload of C:\xxxd\index.js
Status:	Retrieving directory listing of "/"...
Command:	TYPE I
Response:	200 Type set to I
Command:	PASV
Response:	227 Entering Passive Mode (xx,xx,xx,xx,xx,216).
Command:	LIST
Response:	150 Opening BINARY mode data connection for file list
Response:	226 Transfer complete
Command:	TYPE A
Error:	Disconnected from server: ECONNABORTED - Connection aborted
Error:	File transfer failed
Status:	Resolving address of xx-xx.co.uk
Status:	Connecting to xx.xx.xx.xx:21...
Error:	Connection timed out after 20 seconds of inactivity
Error:	File transfer failed

What I Expected/Wanted

ProFTPD to upload a file as it did 2 hours ago, and (almost) every time before that

Please describe what behavior you wanted to achieve, what you expected to see.
Sometimes the "bug" is simply that ProFTPD is doing something different than
what you expected, and sometimes the desired behavior can be done using
different approaches. And sometimes, knowing what you expected to see helps
us to better pinpoint the root cause of the problem/issue.

ProFTPD Version and Configuration

ProFTPD 1.3.7c
Ubuntu
LINUX [Linux 5.15.0-91-generic x86_64]

Please help us reproduce the problem/issue you are encountering. To do this,
we need to know which version of ProFTPD you are using, how it was built,
etc. The following command is an easy way to get all of this information:

proftpd -V

In addition, we need to see all of the ProFTPD configuration files you are
using (minus any sensitive information like passwords, of course). Armed
with the version and configuration data, then, we can set up ProFTPD locally
using the same configuration, and see what happens.

#
# /etc/proftpd/proftpd.conf -- This is a basic ProFTPD configuration file.
# To really apply changes, reload proftpd after modifications, if
# it runs in daemon mode. It is not required in inetd/xinetd mode.
#

# Includes DSO modules
Include /etc/proftpd/modules.conf

# Set off to disable IPv6 support which is annoying on IPv4 only boxes.
UseIPv6                         on
# If set on you can experience a longer connection delay in many cases.
#IdentLookups                   off

ServerName                      "Anything"
# Set to inetd only if you would run proftpd by inetd/xinetd.
# Read README.Debian for more information on proper configuration.
ServerType                              standalone
DeferWelcome                    off

MultilineRFC2228                on
DefaultServer                   on
ShowSymlinks                    off

TimeoutNoTransfer               43200
TimeoutStalled                  600
TimeoutIdle                     1200

DisplayLogin                    welcome.msg
DisplayChdir                    .message true
ListOptions                     "-l"

DenyFilter                      \*.*/

# Use this to jail all users in their homes
DefaultRoot                     ~

# Users require a valid shell listed in /etc/shells to login.
# Use this directive to release that constrain.
RequireValidShell               off

# Port 21 is the standard FTP port.
Port                            21

# In some cases you have to specify passive ports range to by-pass
# firewall limitations. Ephemeral ports can be used for that, but
# feel free to use a more narrow range.
PassivePorts                  49152 65534

# If your host was NATted, this option is useful in order to
# allow passive tranfers to work. You have to use your public
# address and opening the passive ports used on your firewall as well.
# MasqueradeAddress             1.2.3.4

# This is useful for masquerading address with dynamic IPs:
# refresh any configured MasqueradeAddress directives every 8 hours
<IfModule mod_dynmasq.c>
# DynMasqRefresh 28800
</IfModule>

# To prevent DoS attacks, set the maximum number of child processes
# to 30.  If you need to allow more than 30 concurrent connections
# at once, simply increase this value.  Note that this ONLY works
# in standalone mode, in inetd mode you should use an inetd server
# that allows you to limit maximum number of processes per service
# (such as xinetd)
MaxInstances                    30

# Set the user and group that the server normally runs at.
User                            proftpd
Group                           nogroup

# Umask 022 is a good standard umask to prevent new files and dirs
# (second parm) from being group and world writable.
Umask                           022  022
# Normally, we want files to be overwriteable.
AllowOverwrite                  on

# Uncomment this if you are using NIS or LDAP via NSS to retrieve passwords:
# PersistentPasswd              off

# This is required to use both PAM-based authentication and local passwords
# AuthOrder                     mod_auth_pam.c* mod_auth_unix.c
# AuthOrder mod_auth_file.c
AuthOrder mod_sql.c

# Be warned: use of this directive impacts CPU average load!
# Uncomment this if you like to see progress and transfer rate with ftpwho
# in downloads. That is not needed for uploads rates.
#
# UseSendFile                   off

TransferLog /var/log/proftpd/xferlog
SystemLog   /var/log/proftpd/proftpd.log

# Logging onto /var/log/lastlog is enabled but set to off by default
#UseLastlog on

# In order to keep log file dates consistent after chroot, use timezone info
# from /etc/localtime.  If this is not set, and proftpd is configured to
# chroot (e.g. DefaultRoot or <Anonymous>), it will use the non-daylight
# savings timezone regardless of whether DST is in effect.
#SetEnv TZ :/etc/localtime

<IfModule mod_quotatab.c>
QuotaEngine off
</IfModule>

<IfModule mod_ratio.c>
Ratios off
</IfModule>


# Delay engine reduces impact of the so-called Timing Attack described in
# http://www.securityfocus.com/bid/11430/discuss
# It is on by default.
<IfModule mod_delay.c>
DelayEngine on
</IfModule>

<IfModule mod_ctrls.c>
ControlsEngine        off
ControlsMaxClients    2
ControlsLog           /var/log/proftpd/controls.log
ControlsInterval      5
ControlsSocket        /var/run/proftpd/proftpd.sock
</IfModule>

<IfModule mod_ctrls_admin.c>
AdminControlsEngine off
</IfModule>

#
# Alternative authentication frameworks
#
#Include /etc/proftpd/ldap.conf
#Include /etc/proftpd/sql.conf

#
# This is used for FTPS connections
#
#Include /etc/proftpd/tls.conf

#
# Useful to keep VirtualHost/VirtualRoot directives separated
#
#Include /etc/proftpd/virtuals.conf

# A basic anonymous configuration, no upload directories.

# <Anonymous ~ftp>
#   User                                ftp
#   Group                               nogroup
#   # We want clients to be able to login with "anonymous" as well as "ftp"
#   UserAlias                   anonymous ftp
#   # Cosmetic changes, all files belongs to ftp user
#   DirFakeUser on ftp
#   DirFakeGroup on ftp
#
#   RequireValidShell           off
#
#   # Limit the maximum number of anonymous logins
#   MaxClients                  10
#
#   # We want 'welcome.msg' displayed at login, and '.message' displayed
#   # in each newly chdired directory.
#   DisplayLogin                        welcome.msg
#   DisplayChdir                .message
#
#   # Limit WRITE everywhere in the anonymous chroot
#   <Directory *>
#     <Limit WRITE>
#       DenyAll
#     </Limit>
#   </Directory>
#
#   # Uncomment this if you're brave.
#   # <Directory incoming>
#   #   # Umask 022 is a good standard umask to prevent new files and dirs
#   #   # (second parm) from being group and world writable.
#   #   Umask                           022  022
#   #            <Limit READ WRITE>
#   #            DenyAll
#   #            </Limit>
#   #            <Limit STOR>
#   #            AllowAll
#   #            </Limit>
#   # </Directory>
#
# </Anonymous>

# Include other custom configuration files
# !! Please note, that this statement will read /all/ file from this subdir,
# i.e. backup files created by your editor, too !!!
# Eventually create file patterns like this: /etc/proftpd/conf.d/*.conf
#
Include /etc/proftpd/conf.d/
Include /etc/proftpd/sql.conf

[martinnaj]

It seems the issue is IP related, connecting locally through VNC viewer to my other machine seems to work