If you are referring to me, there is nothing wrong and my probe isn't moving. Mines been set up for almost 2 years like that. My point was they will bounce like that. Like looking at mine right now, its set to 87 degrees and its running at 78% power. Now it drops to 86.9 and its ramped up to 80% power, now 83% power. Then it hits 87.1 and it will drop to 0% power. Then once it cools down 0.1%, it will jump up to 100% power for a few secs, then down to 76% and you get the idea. My point was they normally will jump around.
I think what Eric was referring to was if it moves as in your snake buries it with his body under substrate, then it will run forever trying to heat that substrate, or if your snake lays on the probe, it will try to heat forever also. Or of it somehow gets moved across the cage. Mine cant do that though as its through a hole on the left side of the cage(hot side) and its rigged so it can only swing if the snake bumps it while crawling around.