I agree with CA Traveler, I think it's a bad connection. That bad connection could be at the splitter, in front or behind the bedroom wall plate, or on back of television itself. Maybe, the short cable between TV and wall outlet is bad.
Maybe, the TV setting is in cable vs over air mode.
It's possible, the bedroom TV has a weak tuner. They are not all created equal. I have noticed a difference in reception between living room and bedroom, but, it's the living room that gets fewer channels. That TV is older than the bedroom TV.
It's also possible, there has been some mod or picture hanging event that drove a nail or screw through the cable running inside the wall.
It's true, digital signals are not particularly fond of splitters, however, unless the splitter is bad, it is not to the point of dislike where it would not work at all.