EDIT: Just had a game in the 32-bit client and it happened again. It might be this targeting delay thing the confetti item is for. I haven't played in a while.
I just installed the 64-bit client and have played two games with it.
In both games I've had momentary lock ups (usually 1-2 seconds, one was much longer) multiple times during each game
It seems to happen when certain skills are being used by either me or other players. Last game it happened when I was playing PR and used W, also had a Chronos in game it would happen when he dropped ult.