Thanks for the video. This is effectively what we used to call “white flash” even if it’s not really this.
Before posting last post I tested all combination. I confirm some are worse than other, but they still unplayable. The most stable is for me 45fps locked ASW OFF (CTRL+2) as I have “only” one violent flash each 2 to 3 seconds. I’m glad I don’t have any epilepsy problem.
If I unleash the beast (CTRL+1 = no fps lock no asw) my fps raise to around 60 and flash are several times per seconds (yes).
With locked 45FPS ASW ON (CTRL+3) flash happen nearly each seconds, and each 2 or 3 seconds with CTRL+4 asw on auto no fps lock.
In summary if I can lock the sim at one fps no asw pretty sure it will be rare 
I’m joking but I’m angry in fact, very angry as this problem come from the very beginning of VR with MSFS and it’s getting worse and worse, and I don’t see any will to definitively fix it.
For me this simply signify the flash happen more often if you have more fps (asw on mean 90 fake frame), and less if you go down. Sound logical, but the bug still here.