I am having similar problems with Windows 10 File Explorer, in that being able to select multiples files and/or a range of files "STOPS" working after doing it for a while. It seems to be occurring in the past year or so in Windows 10, but I never saw it in Windows XP, 7 or 8.
I have checked the File Explorer Options -> General tab -> and "Double Click to Open an Item" IS selected and File Explorer Options -> View tab -> "Use Check Boxes to Select Items" IS un-selected when the problem occurs.
To explain a little further, I typically run 2-4 File Explorer windows at a time. I will have one File explorer open to C:\... and 2-3 Files Explorers open (one each) to 2 or 3 external hard drives. I may be copying and/or moving files successfully for a while selecting "multiple files" and/or a "range of files" and then copying and/or moving files between drives.
After several successful copies/moves, it stops working and I can NO longer select multiple files or a range of files. NO error messages are displayed. I select the 1st file and then when I select a second file (Cntl-select) or the 2nd file in a range (Shift-select), the first file de-selects I end up with just a SINGLE file selected.
When I check the File Explorer Options -> General tab -> and "Double Click to Open an Item" IS STILL selected and File Explorer Options -> View tab -> "Use Check Boxes to Select Items" IS STILL un-selected.
If I then go to one of the other opened File Explorer windows, I can still select multiple files or a range of files and copy/move them (at least for a while until the problem re-occurs in the next File Explorer window).
However, if I close the File Explorer session (window) and re-open a new File Explorer window, selecting multiple files and/or a range of files work again (for a while). This is OK for a temporary "work-around", but File Explorer needs to be fixed.
And obviously, if closing a single File Explorer and re-opening works to correct the multiple file issue, then re-starting the computer also works to correct the problem (for a while).
I have seen posts back to 2018 about this failure to select multiple files and/or a range of files and it is now 2021 and I am still having the failure.
Any plans to fix this issue? Or at least a "reasonable work-around" (not involving editing the Registry) until it is fixed?