Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.
First, try an incline calibration:
1. remove safety key2. press and hold the speed+ and stop keys at the same time3. Put the safety key in/on and release the keys4. press stop once5. hit the incline + arrow and let the incline go the whole way up and down6. remove safety key
7. Put safety key back in and try running the treadmill again.If that does not work then you will need to check the main harness running down the frame for and damage to the wires or a loose connection at either end.
Let me know what you find...
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