Hi,
I don’t know, if this is the right place for the topic, but here is what I discoverd:
If you try some silly configuration for custome objects like this:
You can’t make an database update. It simple does nothing in the webfront.
If you watch close the log file, you can find something like this:
E, [2019-12-04T14:33:42.208565 #19364-47005678008820] ERROR -- : PG::StringDataRightTruncation: ERROR: value too long for type character varying(20)
Maybe it would be nice, to have a error message in the webfront.
Cheers 
P. S.
I 
your work