Bally solid state pinballs often use .05uF capacitors across switches that
are likely to have a short duration switch closure. The capacitor lengthens
out the time that the switch appears to be closed so that it can be
detected. Otherwise the closure will be missed on fast switches such as
standup targets. The capacitors will fail eventually and may short out
causing the switch to appear to be always closed. The quick fix for this is
to remove the capacitor.
If you find that some of your targets are not scoring during the game but do
during switch tests, then you may have missing capacitors. Also look on the
bottom of the cabinet for capacitors that have been clipped off--this will
indicate that you may have switches with missing capacitors.