I've got the same NVR and have not had any reboots. I'm running 6 cameras, with 24x7 recording, IVS and external alarm events. Seems to me that either your nvr is defective, or there's something different in how it's being used. That could be in how it's configured, the cameras, the power source, ambient temperature, even something as obscure as an unintended ground loop. Just have to figure out what's different. (Easy to say!) For the one where the reboots are related to IVS events, could you take it down to that one camera only and see what happens? Does it happen with IVS events from only one camera or from any camera? Have to find a way to isolate the problem.
I've got the problem of dropped frames on event triggers, which apparently doesn't happen to everybody. I've been "pulling my hair out" trying to isolate this one, with no success so far.