Using the generated RBA module, the __assign function in the root class calls the getModuleRightsOf function, and checks the resulting array for the $r[access'] value. But the array has an $r[rbaccess'] item instead.
I see the same error in all the generated RBA forms: mantain_users, mantain_group, mantain_application, etc.
I'm using last preview build (as of this date)...
You are right. The generated RBA modules are based upon the standard tables, but in our case, we did not use the standard field names. It should work out of the box, so sorry about that. We are currently looking into a way of making this dynamic and have it based upon the RBA class. Created an issue in the BT, but for now you can only fix it by manually edit the code.