I just posted this reply in a similar post, but I had the same problem and
gave up trying to have the dealer solve the problem (4 trips and not once
could they fix it). The first thing I noticed on mine was the ground was
a little loose so I started by cleaning it and tightening it. Didn't help
much, still there. Next thing I did was removed the rubber boot on the
cable end for the ground, it seemed like the rim around the face makes it
hard to get a good connection. You can trim the ring down with a razor
blade but if you're not careful you'll end up removing it anyway.

Next I put in a second ground strap (using 4 gauge wire) from the motor to
the chassis, using the same mount point on the motor and picking a new spot
on the chassis after cleaning it to the bare metal. I also ran a second
ground from the battery to the chassis and a second ground from the
battery to the motor (I was able to do this with a slightly longer bolt in
the battery, not to long or you'll crack the case. I also removed that
rubber boot like mentioned before so it worked out better). After all
these were checked for continuity, I cleaned the ground block which is
behind the left headlight. Finally I sprayed all the connections, motor,
chassic, and ground block (not the battery post) with some gloss black
spray paint, this slows any corrosion and rust from forming.

Yeah, this seems a little drastic having all the ground connections, but I
also have a high end stereo system and this helps eliminate noise. You may
be able to get away with a second ground from chassis to motor only. The
extra grounds may also help eliminate any ESD fluctuations that can occur,
which I believe was also happening to me when it was raining and wet
outside. It's a cheap and easy fix (any automotive parts store should
have pre-made ground straps for cheap).