I'm wondering if those "springs" might be sprung. Maybe see if you can put in a shim or something to make them tighten down more.
When my husband flipped it around, it put a lot less pressure on the unit, and turns out it needed a lot of pressure on it to keep it in place.
We are off to the "big city" to look at a treadmill - every time my husband would say "I'm contacting someone about a treadmill" - I'd catch myself thinking -we don't need any more treadles!