I have had my 2019 1500 for two months now. The check trailer connection alert started 1 month ago. I took it to the dealer and they cleaned and greased the plug. Happened again, they ordered and replaced the plug. Cleared it up for about two weeks, problem started again two days ago.
This morning I sent the dealer a video of the symptoms to make sure I was explaining it properly.
I had the same problems with my 2014 1500.