Weird behaviour

This has me baffled. My small boat has a Lowrance 4 Elite DSI. It works great except for 1 repeatable situation. On a lake I frequent there is an area maybe 50 yards square. When passing through this area the display goes berserk and sometimes is totally blank. If I restart it while in this area it remains messed up. If I revert to factory settings it works correctly for 5 min or less. If I leave the area it will correct itself and all is well. What the heck???

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EMI

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Makes sense. Large power lines pass over this area.

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