Found the problem. In the /saves directory there was still the original map used when I started the server. From then the server used the _autosave files. But apparently the server will scan all maps in the saves directory and will have a problem parsing this old map format, even though he is not us...

Yes, I played the game extensively in each version ...

What do you mean by having the correct save selected? I just copy the "saves" directory to the new version....

Yes I did. My upgrade path was:

Created server 0.17.79
Upgraded to 1.0.0
Upgraded to 1.1.19
Upgraded to 1.1.21 #failed

I tried to upgrade my mega Factorio 1.1.19 headless linux server to 1.1.21 but it does not start. startup.log: 0.736 Error ServerMultiplayerManager.cpp:91: MultiplayerManager failed: "Map version 0.17.79-0 cannot be loaded because it is lower than the minimum input version (0.18.0-0)." I a...