Could just be the quality of the tuner in the TV. I assume that you are doing a re-scan of all of the channels so that the TVs can learn which signals are available in the area that you are in.
Also, from what I remember in my camper, the booster by the main TV has to be on for the TV in the bedroom to get signal.
The antenna connection is right behind the living room TV, the cable to the bedroom is some 25 feet long. This will make a small difference, but if there is a big difference in signal then I would check the connections as suggested above.
Have you done the channel tune on it? They are separate so even if you do living room you have to do the b room tv also . I hadn’t that issue on my unit Same model