This has happened to me a few times now on different days. I'd guess it's happening about once every 10-15 matches. Haven't noticed a pattern yet. (I am also getting random crashes to desktop, but that's been going on for many patches)
It doesn't start until mechs start shooting at each other, but not long into the match the game will act choppy. It's not rubber-banding. The screen freezes completely for about 1 seconds, then instantly jumps ahead to where everything should be.
After it starts It happens every 4-5 seconds so I'm wondering if it's related to a specific weapon sound effect.