Apparently, you decided not to go that direction.. But since you're using a BETA version of Win10, you'll need to describe your problems to Microsoft. That's what the Insider Preview beta tests are all about.. Have you done so? They may have answers for you and maybe a new release that fixes the problem.
In the meantime, have you tried running Chkdsk /f /r /x from an elevated command prompt? We've found it is fixing a number of strange glitches like yours. Tried using a different mouse?
Hope this helps.
Grif
I am running Windows 10 RS3 Insider Preview build 16188 and my File Explorer crashes when I right click items in the left Quick Access bar, like Documents, Pictures, etc. But when I right click This PC and items in the bar under that, they work. File Explorer automatically restarts when I click the top items.
WHAT I'VE TRIED:
-Clicking Clear in File Explorer options.
-Clicking Restore Defaults in File Explorer options.

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