Ok, so the devices are at least working to some extent
Either of those is a possibility.
Ok, the main suspects there for me then are
- a physical connectivity issue
- e.g. if there’s a small break in an internal wire in your tether that loses connection when the tether is under tension during operation, although that would also cause issues with your video stream and general communications
- a power supply issue, preventing the sonars from working properly
- the 5V supply should be quite stable, so if this was the case I would expect it to mainly affect the Ping360
- some electrical noise (e.g. from the ESCs) that’s interfering with the signals between the sonars and the onboard computer, but only happening when the vehicle is being controlled in the water
- you could confirm this by holding the vehicle underwater while it is disarmed and seeing whether the sonar communication works as expected
- there are some suggestions in this comment on electrical noise avoidance and mitigation
It’s unlikely the data amount is an issue, because the data rate from the DVL is generally quite low compared to the telemetry and video information.
You could confirm whether this is the issue by disabling the DVL and seeing if the problem remains.