https://support.chess.com/en/articles/8584209-how-do-i-fix-my-disconnect-lag-issues try this for disconnect or lag issues
Lag

I was playing a blitz game, and I saw my opponents clock hit a few times, but he didn't lose. Is it because my internet connection was bad or was their another reason?
https://support.chess.com/article/423-why-did-the-clock-times-suddenly-change-the-clocks-seem-broken
I was playing a blitz game, and I saw my opponents clock hit a few times, but he didn't lose. Is it because my internet connection was bad or was their another reason?