The frame of the E unit has to be grounded to the chassis via the mounting screw....even if its tight, it could have lost connection.....loosen the screw, wiggle the the unit just a tiny bit, and re-tighten the screw....it’s just a tiny sheet metal screw, make it good and snug, but don’t crank it tight like a cylinder head bolt....that’s the first and easiest thing to check, .....others will have more suggestions.....
Pat