glitch

opponents pieces move atop one another and one cannot make heads or tails of what is going on!!!!

from help:

90% of all technical issues can be solved with one simple solution:

Clear your browser cache! Your computer stores temporary internet files that may be old. If you are having a problem such as "I can't see the pieces" or "My page is messed up" then either clear your entire browser cache, or when on the page with the problem hit "Control + F5" on your keyboard. This will solve most problems.

Additionally, we recommend you upgrade your browser to the latest version. We recommend Google Chrome.

/You are an experienced player here. Have you changed something in your setup recently?

That's like saying "Have you tried turning it off and on again?"

Yes, and no. Clearing the cache is not done when you turn the computer off and on.

It is surprising how often people haven't tried that. 

It's a running joke about how helpful helplines are when you have a problem with your computer.
I'm using ccleaner every day and constantly on private browsing, yet the only site I'm having problems with is Chess.com, so I'm certain that the problem is not on our part.

This isn't the official help desk. However, I assume that the official help desk was motivated to write that comment suggesting that people try clearing their cache and then upgrading their browsers after that strategy had worked 1000+ times.

It may not work for your problems.