The Jensen television volume problem isn't specific to Thor. If you check the Forest River forum you will find folks that have the same issue.
In my Forest River Class C I had 3 Jensen televisions. The only one that had what I would consider normal volume was the one connected to the 5-1 surround sound system which was a FR option.
US Army (Ret)
2020 Entegra Accolade 37TS
2019 Jeep Grand Cherokee Trailhawk (Toad)
FMCA - F432054