I've been using the live replay functionality since I joined FAF, and a couple of times I've run into problems.
Mainly, sometimes the replay desyncs due to the host leaving or a player getting killed which could subsequently lead to a crash (didn't save any logs unfortunatly) or replays simply stop (possibly because the host leaves).
They are not big issues for me personally, since they don't occur every game, but I'd say there is a 1 in 5 chance that problems may arise in a replay.
I can be available for the testing session, just tell me when, I'll gladly help you out!