Please help!

[curious aardvark]

what moves ?
1)The actual print: ie, does it become detached from the printbed.
2) does the print stay attached, and it appear to start printing off to one side.

Unfortunately you've ended up with the current worst printer on the market.

If it gives you the same problem at the same height each time, then it could be related to the bowden tube, or one of the axis belts or gantries is playing up.

Unfortunately the ender 3 seems to be prone to pretty much every single issue you can get on a 3d printer.

Try printing a 15mm square column - make it the same height as the long print.
3 layers: top and side. 15% infill. ).3mm layer height.
Keep the same speed and temperature settings nothing wrong with them.

And see if you have the same issue at the same height with it. shouldn't take more than an hour or so.

Attached stl of a cube thing, resize to correct height in the slicer :-)