This seems like AI_Uboats are in the environment of player's sub. Load the 'Campaign_SCR.mis' into MissionEditor, zoom in your Single mission scenario location and look for them. I'm sure you have mods in use which include AI_Uboats.
If they are created by
Sergbuto, download the latest versions and replace the faulty subs. I think he fixed these sonar/gauges issues recently.
Serg's page
Greetz,
SSB