Up and down usually means toward and away from the work. Is that what’s happening?
If you were using the Rotary tool and forgot to turn it off, you may want to switch it off in LightBurn. There’s a note in the bottom right corner of the LightBurn window to remind folks that it’s still on. ( That’s a pretty wild guess on my part from what I imagined when I read your post. )
We’ll probably need a few more words to get through what’s happening.
This may be worth review: