Also experienced this multiple times, just recently in match 14339572 as the Yamato strafing left.
Interestingly, you can see me try to move right by holding the right key and actually successfully doing so by a tiny amount more than the left movement speed - seems like it isn't a key getting stuck (since that'd apply the same movement velocity no matter what you press presumably) but rather that the movement direction and speed keep getting applied even after the button is no longer pressed.
It always fixes itself after a quick disconnect and rejoin.