Timer increases in ranked rapid bug

I just played a 10 minute no increment game and my (white) timer was changing erratically (increasing and decreasing). My opponents timer was fine.

Looking at the analysis board the timer appears to be working fine until the midgame (08:43) but then it starts increasing and then plateaus around 59:45.

I've saved the game as a study where the timers erratic behaviour can be seen:

Probably your opponent gave you extra time. You can disable this by changing the "Give more time" option in the settings to "Never" or allowing it "In casual games only":

lichess.org/account/preferences/chess-clock#giveMoreTime