It only happens once in a while but the three balls won't release for multiball, you have to shake the machine to get one too release then the others follow.  It never happens when it just has to release one.  Is there an adjustment for this?  Any help will do.

You have to play around with the ramp switches. They need to be adjusted so they just engage as the ball sits on them. This took some time for me to calibrate but once done it works 100%.

The pound of the 3 balls make that,just check the lock shaft and put grease on the shaft

There was also a service message for a 3/8" spacer for that ramp from Williams back in the day. See if the service was done.

http://www.pinball.com/Williams/tech/sb102.htm
http://www.pinball.com/Williams/tech/sb104.htm

Also there were some early software problems with regards to the ramp. It sounds more like ramp angle and switches, but what revision are you running?

Just a simple question, is the game on the right angle as well?

I am willing to bet all three switches aren't being made with three balls up there or one is closing two at a time. They have to just close or else it doesn't work. Just because you say it works properly with 1 ball I would conclude this is a switch adjustment issue. The ramp has room to move fore and aft a bit. It should sit so locked balls are centered directly over the switch and just being made.

Sorry Powerslave I have to disagree, I wouldn't put any grease in there.

You'r right necro but I had the same problems with LOTR and that was only slack on the shaft