I had some similar wild experiences early on in the warranty years. Dealer changed the BCM but to no avail. Strange things seemed to happen more in wet weather. I also did the under carpet check and things were good there.
Then on a random bulb change for the rear turn signal light it would work for a day or two and then blow again. Upon further investigation I found burnt and corroded male and female connections of the circuit board. The circuit board houses all the sockets. All water that runs off the roof and back finds its way in and around the tail lights. I ended up installing after marked circuit boards and soldering in junk yard ( and clean ) connectors for the circuit board. Since I did this, approximately 18 months, no more fancy bells and lights.