Proftpd randomly not writing to transfer log

[RakeshThirunahari]

What I Did

We have transfer log setup in proftpd sometimes during high volume sent on ftp account the transfer log entry is not written for some file for majority of the files it writes the log but not for few.

The only correlation we found that for the files which are missing transfer log have no file size logged in extended log

Files with no transfer log

XXX.XX.XX UNKNOWN ftp_user [11/Oct/2023:13:49:41 +0000] "REALPATH /in/MATMAS20231011134940.xml" 2 -
XXX.XX.XX UNKNOWN ftp_user [11/Oct/2023:13:49:41 +0000] "OPEN /in/MATMAS20231011134940.xml" - 0
XXX.XX.XX UNKNOWN ftp_user [11/Oct/2023:13:49:41 +0000] "STOR /in/MATMAS20231011134940.xml" 226 -

All the files which doesn't have the transfer log have no file size in the STOR command. it just shown as -. Can you please help to know what is happening. Why the files in extended log with no file size are missing in transfer log.

Version 1.3.8

[Castaglia]

For these files being uploaded via FTP, FTPS, or SFTP?

[RakeshThirunahari]

Files being uploaded via FTP.