Unexpected DVL-75 behaviour


I’ve been helping a customer who is having some difficulty with their DVL-75 system. Through remote support I can confirm that their software is setup correctly, with Cerulean Tracker reporting stable communication with the DVL.

The issue seems to be that once a dive is initiated, almost no change of position is registered. Their unit is equipped with the external GPS and gives an accurate initial position, however once submerged the broadcasted position is almost constant, even after having traveled an estimated 10-15 meters. My only suspicion is that the ROV was operating in very shallow water, around 3 meters, and Cerulean Tracker was reporting an altitude of roughly 1.5 meters (resulting in a yellow DVL lock). I’ve also attached the Tracker log, if it is any help.

I’d appreciate any pointers on what might be going on here, thanks!
Log file