I have the same model trailer and probably the same DVD player in my 2007 25RKS. I have not an issue with mine.
As for your other question:
Also, is it possible to run the tv sound through the trailer speakers with an 3.5mm audio cord?
It is possible depending on the type of Outputs you have on your Television and how the DVD player will accept an Input.
My DVD player has a mini USB input labeled as "AUX". If your DVD player is the same, then you will need to locate the Outputs from your Television and take a cable from the television (most likely an RCA) to a mini USB connection on the DVD player.
While watching television, you will switch the DVD player to "AUX" and the audio will come though the surround sound speakers in the Trailer.
Let me know if you have any other questions. I have been doing "Audio" for many years. You can PM me if needed.