I disabled all plugins. It seems it is WPML string translation that is causing the trouble. When I enabled String translation again, I get an error message when trying to save the post field group: Verification failed. (2)
When I search String Translation for the strings in the post field groups that were causing the error, I notice they all are part of domain "Types (obsolete)". Deleting the (obsolete) post field in the post field group solves the problem. It seems someway the upgrade or any other event has caused a problem with the string translation of some fields. This is quite annoying because I probably will have to delete and recreate all these (osolete) fields, unless you can find a way to solve the conflict.
Yes, that's what I meant. At first glance, I don't see any other solution. Luckily, I don't have many data yet as the website is still in develoment phase. Neverthesless, it would be better to find anaother solution. This could happen again.
If this is the case and there isn't many you can go ahead. The only other solution I would suggest is to roll back the versions and try the update again to see if the problem is fixed with the roll back and if it occurs again when the update is done again.
It works again. I had to replace all post fields in this post field group and give them other slugs.
I hope this doesn't happen again because it's a lot of work (replacing the fields, remaking the cred form, translating the new strings,...). Can't imagine the mess it would bring on a live site with many post fields and entries. onTheGo Systems should investigate on this issue with WPML.
