Hi Peter,
thank you very much for posting the problem and especially your solution!
According to your recommendation, I also made a new profile form, which seemed to help until I customized the form. After the customization, I again could not save the profile changes. So I had a deeper look into the customization and my solution for the problem was:
In fields which had the visibility setting “View mode only”, the option “Is this field required” must not be checked. As soon as I unchecked this in all fields, I could save the changes in the profile.
I hope this will be helpful to some other users with the same problem!
Best regards
Momonka