Hi @JochenT
Currently, when you update a field group, every field is saved. If you have many fields and many sub fields, this adds up to a lot of MEMORY and time needed which some servers do not respond well to.
Can you try creating a new field group with only the field group? Does it save correctly? Can you please confirm that the problem is only with saving the field group settings, not a value on a post / page?
Thanks
E
