Context menus not refreshed properly

There is a really nasty bug related to context menus refresh if not moving the mouse once the menu shows.

I've experienced this bug to on versions 5.14.0, 5.14.1, 5.14.2.

1) On versions 5.13.0, 5.13.1, 5.13.2 there was NO bug, demo at https://dl.dropboxusercontent.com/s/0q29e06om06an2i/2020-03-31_16-51-23.mp4

2) On versions 5.14.0, 5.14.1, 5.14.2 there IS a bug, demo here https://dl.dropboxusercontent.com/s/qjg38hy4cxy4ukp/2020-03-31_16-55-00.mp4

I've tested to see if this bug was still present at recent qtbase's origin/5.15.0 and it seems that's still the case... I've checked the logs and I thought 8f88a3962a was a good candidate to fix it but I was wrong and the bug was still present there.

It seems this bug can be reproduced not on both win7 and win8, haven't tested on win10 (don't have it installed). 

Hopefully you'll be able to find the commit that introduced this bug more easily than me. Right now my dev setup is not very good as each build is taking me ~1500s so using bisect is not an option to me unfortunately.

In fact, could you please advice here how to improve the bug hunting on windows where ccache is not an option? How do you guys bisect bugs on your windows environments? For instance, right now each time i checkout a new branch/commit and I try to build... it will just fail if i don't create a new build folder, configure again and jom /j8 ... slow as hell, basically I'm doing cold builds over and over, that's just nuts :/ 

Offtopic: I'd like to let you know there is an error when cloning the qt5 mirror from github, in particular cloning one of the submodules fails, i think qtquick3d.

Thanks in advance.

Ns. I haven't posted the c++ mcve but as you can see it's straightaway to reproduce it.

mcve.py