Intermittent left rear turn signal

Hey all, this may have been covered already. I read a few other threads, but I thought it was worth posting. I have been getting the rapidly blinking left turn signal, intermittently. Seems to be getting worse. Left rear signal is the issue. Tried changing the bulb, no change. I inspected and cleaned the socket, no corrosion, no change after doing that. Swapped the rear sockets and bulbs, they all work on the right rear side. Emergency lights all work, except the left rear. Sometimes when I use the key fob to lock/unlock, all the lights work, and sometimes the left rear does not. I tried changing the fuses in the interior panel and and engine bay, no change.

I read somewhere it could be the signal switch , so I just changed that out. No change. Next I was going to look at changing the signal flasher.

Let me know if you think that would be worth trying, or any other ideas. I am fairly good mechanically, but not great when it comes to electrical issues. I appreciate any help, thanks!