Obviously something is not right. My educated guess would be that either a bell crank is hanging up on something or perhaps you’re missing a spring someplace.
I don’t understand? In the beginning of your message you explain why it’s not stopping, Bc of the VSP. But further down you say that same VSP works great? I’ll need to refresh my memory to the setup.
What about a brake? Since you didn’t include a model number. It makes it difficult to know exactly what it is your talking about. My guess is you have a brake linkage problem.