docker/synology: saasloader error 404

[nrasd]

Hello,
tried to set yobulkdev up on my synology nas using docker GUI ("container manager").

• synology hosting docker, local ip: 10.10.10.2
• container 1: mongo db, ip 172.17.0.6
• container 2: yobulk, ip 172.17.0.4
• I can confirm that mongodb is connected to mongo db

yobulk container config:

{
"CapAdd" : null,
"CapDrop" : null,
"cmd" : "yarn start",
"cpu_priority" : 50,
"enable_publish_all_ports" : false,
"enable_restart_policy" : false,
"enable_service_portal" : null,
"enabled" : true,
"env_variables" : [
{
"key" : "PATH",
"value" : "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
},
{
"key" : "NODE_VERSION",
"value" : "16.17.0"
},
{
"key" : "YARN_VERSION",
"value" : "1.22.19"
},
{
"key" : "MONGODB_URI",
"value" : "mongodb://172.17.0.6:27017/yobulk"
},
{
"key" : "DATABASE_NAME",
"value" : "yobulk"
},
{
"key" : "OPENAI_SECRET_KEY",
"value" : "xxx"
},
{
"key" : "BACKEND_SERVER_HOST",
"value" : "http://localhost:5050"
}
],
"exporting" : false,
"id" : "4b427e6828bbe86e90670d10d33f32b78f09d3a100a73690f5727f707192e7ab",
"image" : "yobulk/yobulk:latest",
"is_ddsm" : false,
"is_package" : false,
"labels" : {},
"links" : [],
"memory_limit" : 0,
"name" : "yobulk-yobulk-1",
"network" : [
{
"driver" : "bridge",
"name" : "bridge"
}
],
"network_mode" : "bridge",
"port_bindings" : [
{
"container_port" : 5050,
"host_port" : 5050,
"type" : "tcp"
}
],
"privileged" : false,
"service_portals" : [],
"shortcut" : {
"enable_shortcut" : false,
"enable_status_page" : false,
"enable_web_page" : false,
"web_page_url" : ""
},
"use_host_network" : false,
"version" : 2,
"volume_bindings" : []
}

I can access yobulk gui on http://10.10.10.2:5050
in step2 of the walkthrough I click on "import csv" which results in error 404. I checked in devtools of the browser and noticed the browser is trying to connect to "localhost:5050" which is unseccesfull. all the other connections in devtools are successfull to 10.10.10.2.
I played around with BACKEND_SERVER_HOST but this didn't change this behaviour.
Am I doing something wrong or is this some kind of bug?

Thank you very much!