Volume and power button huge delays (iPhone 8 Plus, iOS 14.2, no jailbreak)

So sometimes when I'm using my iPhone 8 Plus, there is a huuuuuge lag between the press on the volume or power key, and reaction to this press. For volume key it's 1-3 seconds, for power key it is sometimes up to 10 seconds. And sometimes the phone just ignores it completely.

It's also nearly impossible to take a screenshot too, as home button works perfectly while power button has random delays many seconds long.

The issue appeared (or at least became MUCH worse) with iOS 14.2 update. Erasing everything did not help.

What may cause the issue and how to fix it?

EDIT: Basically, https://www.reddit.com/r/ios/comments/e4wrbl/laggy_volume_buttons_on_ios_1323/ is exactly my issue.

Solution 1:

iOS 14.3 update solved the issue for me. It's still a mystery, but at least it doesn't bother me anymore.

UPD: The issue re-appeared a week later alongside with antennae losing signal (both in 3G only and 4G/3G mode). Turns out, this was a faulty hardware.