I have this problem too since nhl 20.
My problem currently is that I have a constant 20 ms showing in game for many games in a row, but the delay is different everytime. Sometimes, in the same night, it is unbearable. Then another game, it's barely playable. Another game, it is pretty playable. Then back to unplayable. All that with the same 20 ms. For sure, there are some times that the ping is showing 50 ms but suprisingly, it plays pretty well sometimes.
So, I am wondering if the ping showed in game really reflects the real ping. Also, I believe I played against local players.