The hoyer lift that we received on loan from the ALS Association was impossible on carpet. We had the carpet replaced with hardwood laminate flooring, and still had problems with the lift. Then we got new casters. Now the lift doesn't make my wife want to curse at it.
If it's a loaner, the casters are likely worn -- agree w/ B, definitely try to clean them/replace them if needed. Also, like while driving, try to turn/reverse smoothly so the wheels go the right ways.
We got rid of all carpets. Even after we switched to a ceiling lift system (way better than Hoyer lift) the hardwood and laminate flooring helped with everything on wheels, like the Raz chair and medical equipment carts and dollies.
Check the coasters/ wheels. Ours had strands of hair wrapped around them. Must've picked them up ad we go from carpet area to tiles to tiled bathroom. Works ok now on our carpet, but it is low pile.