Clock weirdness
What you're describing is a disconnect from the live server and when it reconnected the actual board state and clock was updated.
https://support.chess.com/en/articles/8584209-how-do-i-fix-my-disconnect-lag-issues
https://support.chess.com/en/articles/8652402-how-can-i-optimize-my-online-chess-performance
This happened 5 times in the last three days: 4 times to me and once to an opponent. I'm using iOS app. This started happening after iOS update, but totally unclear if that is the cause.
Here is the most recent: https://www.chess.com/game/live/121239439460