Generally, VP Jr (25K) or the Mission Engineering are the ones recommended. In the past I’ve used several but prefer the VP Jr because the string design keeps any position extremely stable and doesn’t “wiggle” the parameter. I’m currently using a VP Jr on another pedal and much of the throw is towards the “toe 1/3rd” end, so this may be normal. Not sure if you are expecting perfection.
Any tech should be able to diagnose whether its the proper behavior. Then you could send it in to support if there is an actual issue.
If expression works with the VP Jr. it is almost certainly not the SPACE, generally expression pedals with range adjustment etc are more prone to not being set up correctly.