I guess the problem resides with your ISP. I can say this as I have lost 1000s of bullet games on timeout. Many a times due to lag it showed my opponent's clock was running but it was actually me. Earlier I used to think they are some time cheats. Try playing 2/1 bullet chess.
Bullet chess lag issues


Are you sure? Right now at this very moment, Lichess is down and out....globally.
It's a myth that they have better servers or better connection.

Enjoy these previous threads as well...
https://www.chess.com/forum/search?keyword=Bullet+chess+lag+issues
Hey everyone. I’m a low-level player but I still enjoy playing bullet chess. Lately I have lost several games in the last five seconds of the game. I am wondering if anyone who knows a lot about lag, servers, timers etc. can tell me what the biggest factor is in a typical timeout game? I can’t tell you how often my timer will say that I have two, three, seconds left and I will make a move or even pre-move and still lose on time. Sometimes it will even say that I have lost on timeout and there is still time remaining on my side! Not sure what to make of this. It almost renders bullet chess irrelevant or meaningless, unless you win with ten seconds left or something like that. What good is it if there isn’t a high level of accuracy when it comes to time? Any info would be appreciated. Thanks.