They updated the frame to be less wobbly in early 2020: https://www.fully.com/the-new-improved-jarvis/ (so sibling comment may not apply)

I own that one (extended version) and in the "sitting" position (I assume that's how you would use the wheel) I can make it wobble front to back by a few millimeters if i really lean onto it, but side-to-side i can move it barely a millimeter or two even when yanking it rather hard. It feels really solid in that direction. In the standing position, it does move more.