I have same problem for about 2 weeks. Optical fiber 600/50, connecting by cable, ping in the game shows me 30-40 ms, but the game is practically unplayable, lags even for few seconds, the defender is suddenly on the other side of the pitch. It has always been not so good with gameplay, but now there is a real drama, if nothing changes I throw the game into the corner. I paste results from WinMTR