Same problem here - rear speakers completely out at this point, found water in both door connectors. Right front speaker out most of the time, no water in that connector. Left front speaker now goes out when it rains and just about every morning (dew?). Never lose A post speakers.
Here's what I've done to find out what's going on - cut wire to speaker inside car and ran a new wire through door connector without cutting wire (bypassed connector). No change. So I traced wiring.
Seems that the BCM is cutting out all sound. The BCM is basically muxing audio together so you can hear turn signals, bluetooth calls, etc through the car speakers.
So next I bypassed the BCM. I cut speaker wire to the front left speaker and ran a new wire from the back of the radio right to the speaker. NO CHANGE.
I'm thinking water causes a short in the BCM output so the BCM shuts down all audio output - a safety measure. Does this make sense to anyone else?
If this is right, all shorts would need to found and fixed - sounds like a PITA job but I need to find the real fix for this.
I think the posts on here of people replacing a speaker, the radio, or a wire are all related, they got lucky and replaced what was causing their short. For me, since I have water in the connectors, I'm thinking of installing water tight jumper wires in place of the door connectors.