Timer Glitch, or somehow cheating?

I just played a game where I was able to screen record the last half. The opponents timer literally was going down and then up again, whilst mine just kept going down. E.g. it took about 3 or 4 seconds for his to drop below 15sec remaining, though it jumped from low 15 sec to high 15sec a few times. same in 14 sec and 12 sec. Mine just kept dropping.

Any ideas? I have the screen record to show.

https://support.chess.com/en/articles/8652311-what-is-lag-in-live-chess

Thank you David. I appreciate the link and info. I am familiar with lag, and though frustrating, not something we can really complain about. But their connection was full bars and mine was only 1 down.

It may have looked like full bars, but probably wasn’t on their end - that’s the only reason their time would have gone back up after ticking down, to compensate them for the lag they were experiencing. They don’t get any less time, and nor do you - you actually get more time think during their move