have you heard of ipdb? the documentation is there as it is for most games

http://www.ipdb.org/machine.cgi?id=2238

I just went through my Solar fire drop targets. I would pull the bad one out out and inspect the drop, make sure it's clean/buff the sides with novus. check the latch shelf on front and make sure its not chewed up somehow. check the black plastic guides for burrs or obstructions/dirt. check/replace the return spring. switch that target with another in the bank and see if it's the position or the target itself, or maybe that will fix it. clean and polish the t spring. Polish the two metal bars across the back of the bank. I flipped mine because they never had been flipped before and the inside surface was worn but the outside was perfect, so now they're basically new. make sure the reset bar drops back down on its own after a reset and is not holding a drop up. Make sure there's nothing dropped behind the head of the target in the playfield slot keeping it pushed forward.

Worst case, I have a few spare 3 banks that work ok, taken from a black knight if you need some.

you also might want to check RGP, there is much more history there as Pinside site is fairly new.

You can get there through RGPArchive, or Google Groups:
http://rgparchive-removed.com/rgpforum/forumdisplay.php?f=2
https://groups.google.com/forum/?fromgroups=#!forum/rec.games.pinball

If its a drop target assembly - I have been pulling the entire thing, putting all parts in my sonic cleaner - then buffing etc like JimmyCooks mentions above. They just get gummy and dirty - needs a good cleaning most likely

Ultrasonic cleaner. Great for cleaning plain plastics and metal. Different from a tumbler since it does not polish. Harbor Freight makes a decent cheap model.