Start by looking for anything that can block the slide or add friction to it. Things get wedged around or under it and it won't move. The fact that it "grunts" says that the hydraulic pump is working OK, so it has to be something in the mechanics.
Make of the slide mechanism would help us give better advice. HWH, Power Gear, and Lippert are some common brands.
A thought: are you sure the bedroom slide is hydraulic? Sometimes the BR slide is different than the front slide.