It's not saving due to your condition on the Dykkerinfo tab. You're checking that cb_aktiv is not equal to 1. If it is then you show the tab. cb_aktiv has been conditioned to only be accessible to moderators and also has a condition. It becomes inaccessible during POST and it doesn't exist in POST so it resets. Looks like a possible bug in CB Conditional regarding this behavior.
forge.joomlapolis.com/issues/7048
I think I've a possible solution to fix this. Your test install is setup with the issue so will simply install test builds to see if I can fix it with the solution I've in mind.