I had this EXACT same problem on my Strato-Flite (hundreds worked, no rollover to 1,000 (or 1,000) and then the machine locked up) and mine and hunted it for weeks, lots of switch cleaning and what not. It turned out to be that one or two jones plugs were not in all the way. Pushed them in and it worked perfect...
Although it was having the same problem before I bought it too (I bought it that way), so I think there is an extra set inside of the backbox that aren't removed for shipment or something? Either that or I fixed my problem during my cleaning and the jones plug just simulated the issue as well, but I do believe it was the jones plug.
There is no inside-backbox picture for this on IPDB but check out your game. I remember it was on the bottom right of the backbox, I do believe there was more than just the two or whatever that you plug in when putting the head on. (Sometimes they are used for different units and whatnot that aren't removed for shipping, only service)