Seems like if it's resetting as you press on the new piggyback board some there's still a problematic connection on the MPU.. maybe another pad that lifted or affected trace? A logic probe can sometimes help you find that.. or just beeping things out with the MPU pulled from the machine.
Another idea if you're fooling with Gottlieb System 80B's a lot is to pick up this board off Oshpark (that I shared a while back) and burn an eprom for it if you have the capability. Helps make diagnosing MPU issues a bit easier, especially with Marco's eprom (MarAlb on Pinside). http://www.pinitech.com/lab/gottlieb_sys80_univ_tester.php Link to Oshpark boards if you don't mind doing some soldering and sourcing the components yourself.
Another option I was working on that may prevent ripped traces in the first place but would also be a great diagnostic tool for the problem you're having: http://www.pinitech.com/lab/gottlieb_sys80_piggydeux.php Where it'd be useful is if you just wanted to pull the eprom from the on-board piggyback and put it in this alternate board.. you could verify for sure that the resets are only happening when the eprom is in the on-board piggyback. Unfortunately that one's not available yet, but if it interests you enough then jump on the waitlist for it.
Trying to help make Gottlieb System 80B problems slightly less annoying