yes. I know exactly what u are talking about.. it happens sometimes on my machine.  it is a software glich which happens sometimes.

how to fix.  adjust the rollover switches (usually by bending), check them each in the switch test in the test menu.

make sure the fuse hidden under the playfield (but on the playfield is fine), make sure u have the latest roms in the machine (refer internet pinball data base) and I find that sometimes, if u hold both flippers in, after you make the left or right shot which shld engage the snagger-grabber, the ball actually then rolls to the magnet on the playfield and stays magnetised on the playfield, and then gets picked up.  sometimes, when the snagger shld engage (which only happens if the ball stays magnatised to the round ontop playfield magnet) it doesnt for some reason, i think its a point related software glich, i find pressing the flipper buttons in and out makes the magnet energise and stay energised. I have found that not pressing the flippers most times, allows the magnet not to engage quick enough.

if u cant get the machine working, u are welcome to PM me and I will call u on the telephone and run thru some checks with you.  where are u located ?