Unplug your trailer from shore power and see if that helps...
My older converter did the same thing here if it was turned-on while I was hooked up directly to the battery...
Like said above alot of things are still connected to your 12VDC Battery terminals that can cause interference like this...
You might want to totally disconnect the battery and see if the TV set works fine just connected to the battery without anything else connected.
Of course doing this you may lose your 12V DC signal going to your BATWING built-in Boost Amplifier so your TV signals may go away as well...
Roy Ken