Because you aren't checking b+ while driving however there is one more possibly that lines up with some of your symptoms:

B+ bolt loose. Lift the cover over the aft side of the firewall and check if the bolt going through to b+ is loose. It's how I disconnect power when working on starter/alternator and 1-2x a year somebody on xo discovers their B+ bolt is loose


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2011 E70 • N55 (me)
2012 E70 • N63 (wife)