My 2017 citadel gave me a dash message "rear right signal out" one night, with hyperflash. It had been raining all day and I know there's been a bit of water in my taillight.
The next day the message was gone, no hyperflash.
A few days later my husband noticed that when I signal left or right, both of my rear signals flash together, as if I have my hazards on. The front signals and mirror ones flash normal, no hyperflash on dash, no messages either.

I can't figure out why it's doing this.
I've removed the rear lights, a checked wiring and ground .all looks fine. Initially there did appear to be a bit of moisture but it's now dried out.
Unplugged the battery today for 10 minutes in an attempt to reset my BCM if it had a faulty code still registered, no luck.
I'm really leading to it being somehow water related, but don't know what else I should try. Anyone have this happen?