To complete the sum-up, there is an engine ground strap under the AC compressor that is in an awkward place and could be loose or become corroded (since you are in a winter-salting environment). Worth a quick check.

Nevertheless, it still sounds like a bus communication issue. Grounding connections play an important role but the "standing still vs moving" symptom would indicate a continuity problem.

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.