Have Transmission Questions? Ask a Mechanic for Answers ASAP
There are only two things that can keep the clutch from fully engaging, the clutch disk is to worn for the pressure plate to apply enough pressure to it, or the throw out bearing is hanging on the bearing retainer. I hate to say it but both of these problems require you to pull the transmission out to inspect and repair them.
The hydraullic clutch system is the most simple of clutches. I know you may have just had it replaced, but there are only the two things I posted that can cause your problem. The flywheel could have been machined wrong, the pressure plate could be week, or you could have gotten a defective slave cylinder. I know you do not want to hear it, but the transmission HAS to come back out to fix this problem.
You can not trust everything you see in the internet. I have not ever heard of a clutch not fully engaging working again from slamming on the breaks.
For the clutch not to fully engage, the pressure plate is not applying enough pressure on the clutch disk. If the throw out bearing is not apply pressure to the pressure plate, the pressure plate should be able to hold the clutch disk and keep it from spinning. If it is not, then the pressure plate is bad, or the clutch disk is to worn for it to be able to. I do have a good question for you, when they replaced the hydrollic system, did they use dot 3 or dot 4 brake fluid to refill it?
Did you find your problem?