I have a LMS-525C DF that seems to have a problem. It will be working fine when all of a sudden the sonar looks like it normally looks when you've hit a weed line/shallow water even though I'll be in 20-50 feet. The only way I can get it functioning again is to turn the key and stop the engine. It won't work by just hitting the power switch on the unit and turning it back on. Anybody got any ideas?