Cells randomly stop allowing undo or tab indent

Recently i’ve been finding that cells in my notebooks occasionally stop funtioning properly in the UI (the code is not affected). The main issue is that actionls like “ctrl+Z” and tab indent stop working (tab reverts to showing popup rather than auto-indenting). The cell still runs, and if I delete the cell and move the code to a new cell it all works.

The main bug is that if you select all, Ctrl+X the contents and then make a mistake (i.e. copy something else rather than pasting, you lose work as you can’t “undo” the cut from the affected cell.

I’m also skeptical of the stability of the “text editor key map” - when set to sublime text sometimes it seems to stop and as a result shortcuts such as “Ctrl+d” stop selecting the next occurrence of the selected text and instead it deletes the caret’s line.

I wonder if these bugs are related?

(Should note that it’s not the case where the cell that “dies” (as above) then loses the Sublime mapping, but rather now that ‘a’ cell has died I’ve also noticed that sublime mapping has stopped across the UI)