Luoy,
I was using the beta versions and trying things out.
I was setting up parent child references with contacts being children of companies based on one of your tutorials.
Everything worked.
Then I went to add a new company and got the errors.
I looked at the fields in the field group "properties" and changed the order and names of some fields. I had a repeating field that I changed to non-repeating and it would not save the change. (I can't remember if I did that before or after the companies change.)
I have duplicator files, if that helps: I do not want them available to everyone.