glad path
See the end of this post for the fix that is working for me
small project.
Things i have tried:
(unless noted, nothing changed.)
Restarting Unity
changing font (inter/system) (more on this in a bit)
Ensured no added Editor Scripts are doing anything to cause it.
not running anything doing Task.Run, Thread, or async
at one point even tried more recent versions of Unity
reimported everything.
not using UI Toolkit, aside from what the Editor itself is doing.
Deleted the Library
Deleted obj/ and Temp
at one point, deleted .vs and .sln etc
i have no custom packages installed doing anything. i removed Adobe Substance3D asset to make sure that was not the cause (only thing i had installed that is 3rd party)
restoring Default Layout
deleted the .meta of the script i thought was causing it (just s simple unity event script to DoSomethingWhen i press a key)
tried Debug mode for Inspector
ensured no missing scripts or components on anything
new scene, reconstructed the previous, noted the same issue when i added the DoSomethingWhen script (it is not the script causing it, it just reveals the issue)
In the end, the fix was switching the font Type between SDF and Bitmap.
So far, it has held.