What you see as the same problem on client side may be due different things server side.
When problems appear you fix what you can find and move on. If problems appear again, figure out what's wrong this time, move to fix that and move on. Etc.

You can't always find all problems right away, especially when they appear only under extreme load.

I'm not happy about the situation either, but I recognize that there are limits to what can be done, especially when the people working on it are under heavy pressure.