Frozen screen when alt-tabbing between windows on multiple monitors

 * Cinnamon version: 4.4.6
 * Distribution: Linux Mint 19.3
 * Graphics: GTX 1080 with proprietary drivers 435.21 and/or 440.44
 * 32 or 64 bit: 64 bit

Issue

I have 2 monitors. Sometimes, when I have a game fullscreen on one monitor and alt-tab between that and a window on the second monitor, the second monitor gets frozen. I think this is a problem with the alt-tab program. I am using the Coverflow 3D alt-tab effect style.

Steps to reproduce

This is exactly what I did, but I am not sure which parts are strictly necessary:

1. Have a 2-monitor setup
2. Enable the Coverflow 3D alt-tab effect
3. Load a fullscreen app on the first monitor (For me, it always happened with videogames. I play a lot of proton games and feral ports via steam. I do not know if it needs to be a Vulkan-based game, but I have not seen it with other apps due to not doing this with other apps.)
4. Load a second non-fullscreen app on the other monitor (I always have either Chrome or Firefox maximized. idk if it needs to be a web browser or not.)
5. Alt-tab between the two apps
6. Most of the time, this works fine. But sometimes, when alt-tabbing from my browser on the second monitor to the fullscreen game on the first monitor, the second monitor stops updating. So, whatever the last frame was gets stuck there. However, I can still interact with it. I can drag my cursor over to the second monitor and drag the browser window out and over to the first monitor. But, I am basically doing it blind because I cannot see what I am doing with my cursor or anything that is happening on the second monitor. It stays like this until I restart cinnamon by using the ctrl+alt+backspace shortcut.

Expected behaviour

The second monitor should not get frozen

Other information

Here are the xsession errors: xsession-errors.txt

I think this is an issue with the alt-tabbing functionality in cinnamon and not a driver/kernel issue because, when I restart cinnamon after this happens, the frozen screen becomes unfrozen for a split second as my apps are terminating before the login screen shows up. Also, this happened in kernel 5.0, 5.3, and 5.4 as well as multiple video driver versions.

I have a 144hz monitor with vsync disabled. idk if that matters.

The next time this happens, I will take a video of it.

Start by reproducing the freeze with two monitors, the Coverflow 3D alt-tab effect, a fullscreen game, and a second-monitor browser, then review the attached xsession-errors.txt. Trace the alt-tab behavior involved in switching to the fullscreen app and determine why the second monitor stops updating. Done means repeated switching no longer freezes the second monitor and the existing reproduction steps remain usable.