Strange effect selecting rectangular region

[Angelo Graziosi]

They are few master builds I notice this strange effect. 

Selecting a rectangular region with 'M-C drag mouse-L' produces the rectangular 
region but when the keys (M, C, mouse-L) are released the related lines appears 
in yellows as the attached screenshot. This happens often not always and the 
only way to get that the yellow disappears is to restart Emacs (I have not 
found a recipe to do that in Emacs).

I have seen this on Windows an macOS but not on GNU/Linux builds...

yellow-region.png
Description: PNG image