Walkpad "jerking" when I walk on it, especially on lower speeds. No issues without me on it.

So this is a cheaper Walkpad, though I paid over $250 a year ago, branded Citysports. I do know all of these suck mostly, but the machine worked well and it seems like it's built nicely, though not sure about it's motor.

I am 150 pounds, the machine limit is about 250, so this is not the issue. It jerks a lot, on lower speeds, if I press down on one side with the leg it 100% stops. But even on higher speeds ~ 3 miles slight jerks happen. The issue gets better as I walk on it, I usually walk on 4 miles, and it gets better by the time I end the session (45 min), I believe at around 30 minutes in, these jerks are muuuch less noticeable, but at the start it can be all the time.

It might be that issues started when I loosened a the belt a bit, but I still cannot fit even 2 fingers (which is what is usually recommended). But I am wondering if it could be:

1.) It's the belt (which is properly centered), loosened or tightened.

2.) Lube, needing more? Less? Should I fit a hand (not possible now, need to loosen it further) and what do I look for, should it be all lube up or?

Worse issue, like the motor, or none of these symptoms have to do with it?