Chromium/Opera "randomly" not rendering in i3

I'm on 18.04, using i3, and sometimes when I go from some workspace to a workspace containing chromium or opera, those windows aren't redrawing. I can still press ctrl+s to open a "save to" popup, which renders fine.

The behaviour is quite quirky, and it happens maybe twice a day, and I can't seem to find a way to reproduce it reliably. Here are a bunch of observations:

1. I think I usually have cpu usage of 20%+ (according to mpstat 2 1 | awk '$12 ~ /[0-9.]+/ { print 100 - $12"%" }'), when it happens
2. After it happens, I can't use mod+q (to quit window from i3), ctrl+q (to quit from opera), but I can seem to be able to run ctrl+w to quit a tab, even if I don't see it immediately. When I reopen opera, that tab is gone
3. I can quit the process by running fkill opera, or the appropriate amount of pkill opera
4. About a week ago, I was running ubuntu 16.04 with i3, and I already had problems. I thought maybe getting a fresh install would help, but it didn't. It worked fine for a few days, but after ~3 days, I started getting the errors again, so maybe there's a package that I installed that broke it?
5. Opera/Chromium didn't always do this. It started about 1-2 months ago
6. When it does the rendering bug, it simply shows whatever was occupying those pixels in the previous workspace.
7. I can still open terminals and other windows on that workspace, and they will display just fine. If I then shrink or remove them, the pixels previously occupied by that new window will now have changed to whatever was in those windows
8. the mouse cursor doesn't leave a trail
9. I think it happened with other resource-heavy windows, but I don't remember for sure

I haven't managed to isolate the conditions and versions of the browsers, i3, or other packages. I'm running the latest stable of everything, as far as I know.

From what I can tell, it could be anything from a driver error, to a bug in some package. I'm not even sure where to look for possible logs of this

Any suggestions? Does this happen to anyone else? Should I report this to opera/chrome? Should I also file a bug report for i3? I'm very confused

In my case, it turned out that something was wrong with the GPU renderer of the browsers

After apparently another 2 months after posting the question and inspecting various scenarios, I still haven't figured out why it happens, but I've figure out how to fix it once it happens.

When one of your chromium-based browsers freezes/disappears like that, look for a process with --type=gpu-process under either opera, chromium, or what have you, then kill it

$ ps aux | grep opera | grep gpu-process
user      9736  1.8  1.4 613716 115176 ?       Sl   Jan09  26:35 /usr/lib/x86_64-linux-gnu/opera/opera --type=gpu-process --field-trial-handle=...
$ kill 9736

Some tabs might be affected, and display an error, but simply refreshing them makes the browser work again

Try disabling Hardware Acceleration in Chrome → Settings. This worked for me.