User was getting a weird issue trying to clone some entries- it would do a validation error message, but nothing was highlighted as invalid. After digging, it was objecting to a missing ip_address field- but there was no ip_address form field.
Digging into it, it validates the ip_address from/for the ip_address in exp_channel_titles.
Locally, I tried cloning an entry with a blank ip_address in that field- but that work. Then I stuck a 0 in the field, and boom- replicate.
Not sure why, but user had 0 in the ip_address db column for some of those entries, and if you try to clone those, it acts like there's a validation error. Though you can't see what's causing the error, because ip_address isn't a form field.
Note- tested with ip_address required to post in the settings. But no idea if that's in play- I suspect it is moot.