1. I see a ton of OE parts with various and sundry ‘factory marks’ on them. Maybe they are production markings from the vendor that makes it for BMW??? Who knows... marks..labels..numbers..

2. Maybe the prior owner replaced it in a futile attempt to resolve a CD8B code?

3. Assume you’ve check the harness for nicks, cuts, inadvertent grounds?

4. Could be a loose pin/socket in a connector...your explorations may have jiggled something.

Not much help, but some thoughts