I dont have the Furrion dvd player, I have the iRV which im sure is just as poor. We no longer use it for DVD's. I had a PS3 in the house gathering dust and no longer being used because it was replaced with an Xbox one X. So I moved the PS3 out to the camper and hooked it up to the iRV through an HDMI input. It now handles all our movie playing duties. Being hooked up through the iRV, I still get sound through the RV speakers as well as through the TV. This also gives us the ability to play blu-rays, play games, and stream from Netflix, amazon, Hulu, etc. using either cellular data or the occasional WI-FI if we can get a strong enough connection.
If your looking for something more conventional like a direct replacement,
https://www.crutchfield.com/ carries a few RV/Marine entertainment systems from other manufacturers such as Jensen. But not all play DVD's, and I'm not sure if they would be any better than the Furrion/iRV's originally installed.