It is highly unlikely this symptom is due to a corruption of Gramps application.
The following is PC specific but I expect Macs are similar. (Doing ResEdit cleanups of the Mac's Registry 'resource fork' was a traditional minefield for classic Mac users.) We need a macOS user of Gramps to tell us where the file is stored with the registration of Gramplets. Deleting that file (or just the subsection for the Forms Gramplet) should resolve your problem. Gramps will re-initialize any missing Gramplet registrations.
In the Windows environment, deleting an application and re-installing is just an exercise in futility for problems of this type. That is mostly helpful when the application fails massively after being corrupted or has become cluttered with debris from sequential upgrades.
All the customization is stored in the User area of rather than the Applications area of modern multi-user computers. (This is because things like the Windows security system requires the logged in user must have Admin rights to modify installed ‘All Users’ apps. But they are granted a low security area for installing single users apps & all their personal Preferences. It is relatively OK to foul up your own workspace, but not everyone else’s.) Generally speaking, uninstallers forget about flushing the customizations.
The selection of Gramplet add-on installations is definitely a customization. So, in the best case, we need to locate & delete a single item… the registration of installed add-ons/plug-ins. (Worst case, you can nuke the whole Gramps subdirectory in the user area. That’s a LAST RESORT because you could unintentionally lose some useful stuff that’s painfully convoluted to recreate. This could include archived Tree data.)