Cheaters
I am not a wizard myself, but I know that when I'm playing one online and winning, my internet connection is vulnerable to farfetched surprises.
I haven't been receiving this issue, but I see it's a common mishap. I mean, I don't play live much anymore, so, perhaps it is something to do with your internet, or perhaps just a glitch that you may file a ticket, or just report to a staff or mod.
Though, with contributing to this, I must add that cheating discussion is not allowed on the chess.com forums. If you need to discuss about this issue, I suggest you join this club:
https://www.chess.com/club/cheating-forum
Thanks!
ONLY reason why I say its a cheating method is because I play quick 3 minute or 2/1 minute games. I'll play 2 out of 3 games and the ones that I lose, there is never a problem with. But the some of the ones Im about to win from these same players, all of a sudden the signal gets lost and they win on time!! has happened on many occassions with the same 2 or 3 players!!
As FM_Checkmate mentioned, this kind of discussion belongs in the Cheating Forum, not in general discussion. The symptoms described by the OP are subject of recurring threads, most recent being Time manipulation program used by cheaters?