Before I start, I would like it understood this done incorrectly will start a fire, and destroy your machine, this advice is given with that warning understood
Recently I helped someone with a black cable error, the GF would stay in focusing no matter what he did, it started after he did a cleaning, and may have (may have) gotten some alcohol on to the camera lens on the top of the lid. (I don’t know for sure) He was desperate to get the machine back online, and USPS one day turned into USPS 3 day (add a weekend to that)
So I suggested Unplugging the machine then opening the small lids up on the black cable, and the white cable on the lid, covering the camera with some tape to make sure it does not get hit with spray and spraying all the contacts with contact cleaner (use the tube to be more accurate) then let it dry 4 hours… and IT WORKED he is back up and running.
this is a FLAT FIX solution, it will not always work, and it may do damage…
BUT it is a way that got someone back working.