Maurits said:
You could try disable all 3rd party plugins and try to upgrade, sometimes this will help, if not you will have to contact your 3rd party developer
In this case, it modified default SE database tables and core product files which we don't recommend. Due to that, in order to upgrade properly, the client needs to contact the experts first in order to avoid any issues from upgrading with core and database alterations.
Maurits said:
You could try disable all 3rd party plugins and try to upgrade, sometimes this will help, if not you will have to contact your 3rd party developer
Thanks for the reply, I already tryed this!