I've been using a Therabite for over a year now. The pads do fall off but I just clean them and reattach them with white glue and clip them until they dry overnight.
It sounds like there is a bite issue as if your Mom presses her teeth right up against the little rim shown in your picture, her teeth shouldn't slide. It also sounds like you Mom is biting too hard onto the pads. The speech therapist who gave me mine emphasized that I should only lightly rest my teeth against the white rim and on the pads and not clamp down or bite at all. Instead let the Therbite open and stretch the jaws. In rereading my instruction booklet it does say: [quote]Your front teeth should just touch the inside rim of the upper Mouthpiece. Be careful to hold the jaw mobilizer level. Slowly squeeze the lever. DO NOT BITE ON THE MOUTHPIECES[/quote]
The upper jaw is just one solid piece of plastic so it should not be bending at all. The lower jaw does flex a little but not so you would notice.
Again, I would recheck the settings, especially the white knob at the handle that sets the distances. It turns in an odd way, the exact opposite of what I expected. Try resetting that. Plus check that the pin in the upper Range Setting Arm is at the last hole towards the mouthpieces (it appears that way in the picture you attached.
Sorry for all your problems and hope this helps
charm