msmmike Thank you for providing the Spine project. I have identified the cause. This is not a bug, but rather the result of an option enabled in your transform constraints.
In that transform constraint, the Local option is enabled for both the source bone and the target bone:

This means that when each mix is set to 100, the local translate X and translate Y of bone29 will be applied to the local translate X and translate Y of stickjoint.
Looking at the local translate X and Y of bone29, we see the following:

When you apply these X and Y values to the stickjoint, which is a direct child of the root bone, moves to a position 1.1595 in the X direction and 2.0821 in the Y direction from the position of the root bone. (In other words, it moves to a position very close to the root bone.)
I'm not sure exactly what kind of rig you want to achieve, but if you want the stickjoint to move perfectly along the bone when bone29 is translated, you should set it up as follows:
