Hello. Thank you for contacting the Toolset support.
Well - in order to check whats going on I will require test site.
Can you please share staging site where I can perform the debug actions in order to minimize the cause of the issue.
*** Please make a FULL BACKUP of your database and website.***
I would also eventually need to request temporary access (WP-Admin) to your site. Preferably to a test site where the problem has been replicated if possible in order to be of better help and check if some configurations might need to be changed.
I have set the next reply to private which means only you and I have access to it.
I'm not sure but I just installed the "Toolset Forms" plugin which was not installed on your staging site and I try to create a new post relationship form and I've also enable the expert mode but I can see it working as expected:
=> hidden link
Glad to know that you able to spot and isolate the issue. Can you please check and report the issue to Admin Menu Editor Pro support and check with them if they have any possible fix to share.