Closing 'Palettes' window disables keyboard shortcuts (Master Palette... not affected).

Hello everyone.

I've read how from time to time people have reported that suddenly their computer's keyboard no longer functions in Musescore. Closing and restarting Musescore clears the problem, but then it randomly reappears once more. Suggested explanations have included corrupted scores and conflicts between system language and Musescore's own language engine; and the most frequent suggestion is to 'Reset All Preferences To Default'.
I too have recently started to suffer this issue (hence the background(!)), and resetting preferences to default does in fact succeed in clearing the problem. However, I think I have tracked down the issue.
So, background. I recently replaced the graphics card on my MacBook Pro (Late 2011); enabling me to upgrade my operating system from Mac OS X 10.12 (Sierra) to Mac OS X 10.13 (High Sierra), the highest version compatible with a MacBook Pro of this vintage. Musescore's keyboard shortcuts began to stop functioning after this. So, clearly there were two possible reasons for this: change of OS or bug (undocumented feature(!) ) in Musescore.
I can't obviously downgrade my OS just to test, but in case the upgrade had done something untoward, I cleared Musescore completely from my computer and performed a clean install of Musescore 3.6.2.542080600, and making sure that the language settings were set to 'system' (and system set to English (GB)).
Unfortunately, this did not cure the problem, causing me while editing my score to have to reset Musescore preferences every few minutes or so.
However, a pattern began to appear. The problem would always occur after using the 'Palettes' menu.
(I am having in any case a problem searching 'Palettes'. I can make one search, but thereafter the search window won't accept further input without closing and reopening the Palettes menu).

A few minute's research on the (unedited) version of 'My First Score' (no possibility of corruption!) installed with this clean install of Musescore, narrowed down the problem to closing the Palettes menu.
If I open - and then close - the Palettes menu, all keyboard shortcuts become disabled (including, e.g, the spacebar's 'Start/Stop' function as well as letters for note inputs and numbers for note length). If I close and re-open the score, keyboard shortcuts are re-enabled, without the need to reset preferences.
Notably however, if I re-open 'Palettes', that too will re-enable keyboard shortcuts.
This issue does not affect 'Master Palette', only 'Palettes.'

I hope I have provided enough information for this to be a reproducible outcome (to summarise: I can perform only one search in 'Palettes'; closing the Palettes window thereafter disables all keyboard shortcuts; reopening enables them; no other action has this consequence). I did do a search for this issue before posting, but if I missed it, please accept my apologies. In any event, knowing what's causing the problem makes the workaround in this instance quite simple.