When you precomposed, did you move all the attributes into the new precomp? That’s a vital step for gettng plugins to behave right. If you did and it’s still not working, I’d try rendering the mattes out of Mocha Pro and applying the same speed to them in your host.
Please note, if you’d applied Mocha after the speed ramp you might not have gotten a good track on the shot anyway, Mocha really doesn’t like tweening that speed ramping creates because it adulterates the texture Mocha is trying to track.
If you have any more questions, I will be happy to help you.