I was at the SC last week for this issue. They've told me that it is considered normal operation for the FWD sensors to fail when they heat above 110 degrees, such as sitting in the sun. They also said that darker colors experience the problem more often and that the driver's door seems worse. They're going to install a larger butyl patch which may help dissipate heat. Interestingly enough, they consider the butyl patch a goodwill issue, not an official Tesla warranty fix.
It's pretty clear from their response that if the butyl patch doesn't work, they're not going to try anything else. If the problem isn't improved, I may try an executive escalation, but I'm not sure if there is a real fix. Some people obviously don't have the problem, but it could be some perfect combination of metal thickness, paint, adhesive and sensor tolerance that makes them work or fail.
I could probably lemon the car if they can't fix it, but I like the car and even if they did buy it back, I'm unlikely to find another P100D inventory to replace it for the buyback.
Concern: Customer: States the left Falcon Door will detect false objects after sitting in the
sun.
Pay Type: Goodwill - Service
Corrections: Sensors General Diagnosis
Tested both falcon wing doors and found the ultrasonic sensors and carriers are working
as expected. After reaching a surface temp of roughly 110+ degrees the door panel will
become heat soaked and does not allow for proper sensing of the sensor. This is similar
to heat soaking an iPhone and it not functioning temporarily until it comes back within
operating temps. When operating the vehicle outside of the sensors operating
temperatures it will require you to override the falcon wing doors on the touchscreen or on
the B-pillar switch. To attempt to provide a wider heat range of the ultrasonic sensor we
are going to install a new/bigger butyl patch. Once the door panel cools off and the
temperature comes down the sensor will again work as expected not requiring you to
manually open/close the door.