I have the latest firmware 3.71 but also have this problem. It's been working fine since the update but suddenly at a rehearsel there was no sound. I have the Helix Floor. I switched off the unit and after a couple attempts the sound came back. When I came back home the unit worked fine with no issues what so ever. Yesterday the problem reappeared at rehearsel. Came back home, same problem, no sound. Swiched off the Helix during night and this morning it functioned as normal. I don't like problems that comes and goes. I haven't tried a factory reset but I've read about others that have done it with no luck.
