During the dives I have 2 times up to 5 times a complete loss of the picture (QGC like starting on the computer without tether connection: Waiting for connection) for 3 up to 5 seconds. Last year I had these symptoms during the rest of the dive, so I had to give it to the mechanics. But I think, the real cause of this connection losses are not found. During the camera loss, a second camera continues sending pictures and the I can control the ROV. So it can not be a complete connection loss.
It’s not particularly clear what’s going on here, or what’s causing it. If you’re still able to control the ROV and receive information from a camera then you have at least some level of communication, but perhaps you’re running into bandwidth limitations, or maybe there’s an issue with your camera and/or how you’re powering it.
I’d recommend doing a Network Test (via the web interface) to see what your data capacity is in each direction, and perhaps seeing whether it helps to provide external power to the cameras via a powered USB hub, instead of powering them through the Raspberry Pi USB ports.
Unfortunately if an issue is intermittent it’s quite hard to diagnose and resolve, so unless you’re able to consistently replicate it there may not be much more advice we can provide beyond trying replacement parts and seeing if the problem stops appearing.