In the video you can see that something in this Common Grid is corrupted. I tried moving this button but it semi-copied it instead. And now I cannot clear either of them. This never happens when editing regular grids but is common when editing Common Grids and this is why I don’t use them.
Common Grids_Keyboard - High Tech - Test.mgrid (188.3 KB)
MGP 1.6.19 (35764)
Ah! I’ve experienced similar behaviors on my setup where copy/pasted items actually paste ON TOP of what they’re supposed to replace and create a fixed “double-image” or, like your example, you can see the grid cells underneath the art. And once it happens, it’s stuck that way.
Sometimes just re-installing the grid fixes it, but the only for-sure fix has been to remake the grid. This very thing speaks to something I was actually going to post about. It’s a behavior that’s not limited to MGP. Every app I use that relies on templates or elements that are repeatedly moved or edited accumulates gremlins in those files over time. Pro Tools used to be so bad that Avid themselves told people to just re-build their template if certain problems were occurring. Cubase is also notorious for this. A template file will progressively keep doing stranger and stranger things over time and usually all of them are inexplicable. The solution is to just make new a template and poof, everything is back to normal.
It’s caused me to adopt a certain level of “template hygiene” 
over time. I refresh my DAW templates annually and as for MGP, if a heavily used grid or template is over two years old, it gets rebuilt. And with the rate of updates as fast as it is, I’m probably going to move to annually at minimum. I also do a full re-install of MGP every three months or so as a matter of course. Between the OS updates and the app updates and comms between the tablet and computer, stuff gets kicked around in the background. It’s all minor things, but they accumulate and start to cause problems.
That might be part of why your copy/paste is broken. It may not. But a refresh of the scenario is an easy task and might solve it. I’ve found that sticking to that practice has resolved many more issues than I ever thought it would.
I’ll see if admin have the same issue with the grid I posted above. If not, I might consider your suggestion of a rebuild at some point. 