Reference image moves "around" objects instead of sliding through them I am new to Blender, trying to work through the BlenderGuru tutorial here.  I have loaded the reference image of a coffee cup and would like to shape a cylindrical mesh to model the cup.  When I try to move the reference image, though, it seems to automatically move "out" in the y direction, as if it is sliding around the cylinder.  If I move it back to where its y coordinate is 0, and again try to move in the x direction only (using "g" and then "x" to slide in that direction), the y coordinate also changes.  Any thoughts on what is going on here?  It seems there is some physics constraint it is trying to enforce, which keeps the center of the reference image from entering the cylinder.

The image below shows my starting point.  The "Object Properties" window on the right hand side shows the y coordinate is zero.  The image has been oriented to the front by clicking numberpad-1.



When I try to move the reference image by clicking "g" and then "x" and then dragging toward the left, the intersection with the cylindrical shape clearly changes.  When I look at the "Object Properties" window, I see that the reference image has moved forward on the y axis, which I can confirm when I change my viewport to a side view.



Any pointers as to what is going on here, and how to fix it?  Thanks.
Disable the Snap option (magnet icon on the top menu bar), if you enable it, it will make the object you move stick to the selected mode.