Setting server to older update

[judos]

As I understand save files broke recently, I also get the error on my server which i just restarted now:

Using beta legacy_update_1 without a password!
[LOG][1] 000:00:00:  Foundry CL:20868 (RELEASE)
[LOG][1] 000:00:00:  Configuration: Stable
[LOG][1] 000:00:00:  Platform: Steam
Success! App '2915550' fully installed.
Unloading Steam API...OK
steam_appid: 983870
[LOG][1] 000:00:00:  SettingsSaveData.validateAndCorrect: different game version(0.5.2.16455), setting new values.
[LOG][1] 000:00:04:  Loading existing dedicated server save file from World DockerLuxusburg: j10.
[LOG][1] 000:00:04:  ERROR: Failed to load save file: world=DockerLuxusburg, save=j10

This is even so i'm using the beta branch with env variable in my docker-compose:

environment:
      - BETANAME=legacy_update_1

However on my client the save loads just fine with the legacy_update_1 version. So am I doing something wrong with setting the server to the old branch?
The log "Foundry CL:20868" sounds weirdly like the newer build version, since my client says 0.5.2.16455 with the older build version.

Any idea?

/edit: found this file ./server_files/version.txt with the content:

0.6.0.20868

With seems indeed something with setting server version is wrong.

/edit2: Still works when i use the older image v1.5:

services:
  foundry:
    container_name: foundry
    image: luxusburg/docker-foundry:1.5

./server_files/version.txt:

0.5.2.16455