Yeah it used to be very well behaved, could go back and forth 2D/VR several times in a session and all was good. Recently it’s often not, and switching can give extremely poor performance outside the realm of reasonableness.
One thing that worked for me a few times, is if I get bad 2D perf after switching, shut off the WMR portal, and it’s back to good. Haven’t extensively tested any of this to know how consistent any of this is but that is one that that worked at least a few times for me.
I have the exact same issue! Does anybody know how to fix it? My issue is I start in VR on a long flight, toggle out of VR and go do something else, come back and crash into the runway because the lag is so bad. Also on a 3080TI with a 9900k Windows 11 32GB RAM. Performance is the same in VR after toggling in/out as it was on my 1080ti.
I fixed that problem by matching my PC and VR graphics settings.
My PC settings were initially much more demanding/agressive than for VR. I feel like handling that transition is what was causing problems. I would often get 4fps switching back into VR during a flight.
MS Store version
Logically, it will be difficult for programmers to improve since MSFS looks better and better. Think about what happens when you suddenly jump from low-detail VR mode to 2D with different settings. The small amount of memory of the graphics card has no place to quickly put this amount of scenery with different settings. So the first thing you should do if you want to fly in VR is to adjust the settings for PC to those of VR. The more memory the graphics card has, the more this type of switching will be tolerated - e.g. 3080 I had these problems and with 4090 there are almost no such problems. I write almost because there are scenery where the jump from VR to PC tragically beats the performance even on 4090, unless I have the same PC / VR settings.
On mine, when I switch sometimes, WMR changes the focus to some other app, and the screen goes to desktop, with all windows, including the game, running but minimized. This is from peeking out under the goggles. I have to hit alt tab until the game window is highlighted, then the performance comes back in VR. MSFS doesn’t do well when the game app is not in focus and something else is, like LNM, or Discord.