Internal Server Error for all users but Admin

Just installed this plugin and applied settings etc. But now I get ‘Internal Server Error’ every time anyone with any other role than Administrator logs in.
I deactivated the plugin and they can login again. Any ideas as to what causes this?

I use this plugin as a replacement for the other ‘User role editor’ (https://ww.wp.xz.cn/plugins/user-role-editor/) which I have removed. May it be that there are some leftovers that cause any conflict?

Thanks in advance, cheers,
Leo

https://ww.wp.xz.cn/plugins/wpfront-user-role-editor/