> Hmmm, this may just be a chance thing or maybe due to some other factor. Did you possibly update your video driver recently or switch off transparency for the Windows desktop theme or anything like that? Because as far as I know I haven't done anything in particular to solve this myself...

No... Neither I recently updated my video card driver nor changed any windows transparency settings.

I downloaded and installed v2 to see if I can reproduce this again. And yes, I did reproduce this bug easily with v2.
I captured a video. Please check it out: http://www.youtube.com/watch?v=sFCwsElV96U

In this video I merely open the file. I did not click anywhere when flickering happened, only moved my mouse around.
This used to happen all the time until v3 nov-19 beta.

Now I uninstalled v2 and reinstalled v3 nov-19 beta. Double clicked the same file. Flickering did not happen!

I'm on a windows system but maybe this was fixed unintentionally with this fix??? -> " Fixed a bug on OSX where window resizing behaved strangely on Retina displays."