First thing I'd check would be if the Search Disc is dirty/in need of cleaning. This is the large disc at the right end of the big motor in the center of the bottom of the head. If you see black marks going from rivet to rivet, it needs to be cleaned. Cleaning without disassembly is doable, but can be difficult, especially if you are not a careful person.

Another problem may be that the timer is not stepping up all the way to fourth/fifth position or the ball tracking trip relays are not tripping/maladjusted (maybe because of the timer issue), but take a good look at the search disc first, maybe post a photo. It sounds like the timer and trip relays are moving because you're hearing clicking (the search relays chattering). Dirt on the search disc prevents good electrical contact, and the disc turns at a rate that requires very quick activation of the search index coil (kinda the payout relay in the game - while it is held, games will be added to the replay register). Don't fool with those switches if you can avoid it/ have more experience with switch adjustment - they are very very difficult to adjust properly, and very easy to knock out of adjustment accidentally.

Good luck!

https://www.ipdb.org/showpic.pl?id=1408&picno=40102