Hi there, I have an identical problem on my two early Bally machines.
Neither will tilt, even holding the tilt bob or the tilt bob rod against the lower tilt bob "ring".
However, it will tilt 100% of the time very easily if I am touching any of the grounded metal surfaces on the cabinet (e.g. side rail, lock down bar etc). i.e. It tilts if I move the tilt bob over with one hand and touch the side rails with the other).
Being the genius I am, I thought "this must be a grounding issue" and then ran a jumper from the cabinet ground to the tilt bob, but that caused a small spark and I think a game reset (this was a while ago).
I don't know what to make of this. Given I have the same behavior on two games, I thought this might be common enough I could find a fix for this online, but no luck so far.
Thank you for reading, and any help will be appreciated!