I encountered that once way back in the early days of developing the new installer. IIRC it was caused by a permissions issue with writing the progress-meter file, which seemed odd. I was certain we'd fixed that though. So your case might be caused by something different.
Another thing which I'm sure was fixed was that the progress-bar is a modal which originally could be "canceled" by clicking anywhere else on the page to close the modal ... and of course then the installation would halt. But that was fixed, and besides, if it was still happening then you wouldn't be telling us a percentage because it would have disappeared from the screen.
Another former observation is that the percentage bar doesn't always get to 100% because it's being read from disk and sometimes things complete before it can read that final 100 value, and so it jumps to the next screen without showing 100%. But that's not quite what you're experiencing either.
Usually when zc_install encounters a "fatal" problem, it will log into the /logs/ folder with a different kind of filename: zcInstall-DEBUG-xxxxx.log (note the word DEBUG), in which you'll find the details of a PHP or MySQL error that's caused problems.
I'm puzzled by yours isn't triggering the debug file if it's failing to complete normally.
I realize this post doesn't give a concrete solution to your situation, but perhaps helps inform you more.