I went diving with my computer my aunt gave me used. Everything worked well for the first dive except the computer never changed the depth as we swam up. I reach 95 feet. When I went in for the second dive the computer just keep logging deeper and deeper number ending up somewhere around 230 ft 2nd dive never got below 50ft. Air tank reading we correct the whole time. Has anyone seen this issue or can help me understand what happened? Is this just a bad unit?