Eliminate mechanical binding as the issue first.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Like Chris mentioned, this is usually a stuck diverter mechanism, there are subway diverter tests accessed through the test menu, you should be able to hear these when the fire. The diverters are metal-metal contact and were greased at the factory. This grease being 20+ years old will gum up and keep the diverter from operating properly. Dissemble, clean with your choice of cleaner and reassemble. I do re-lubricate these with a tiny bit of Super Lube PTFE grease.

I believe that the OP is talking about the diverter that loads the Borg ship vice the dual diverters under the PF.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

My delta ramp diverter became clogged/gummed up after so many years and prevented the mechanism from moving at all. Disassemble and clean as pin_guy said should take care of your problem. Mine works silky smooth now.

Thanks Chris, most of the same applies for the diverter, but it's also likely that the delta ramp gate switch is not registering the ball entering the ramp so the diverter is never told to operate.

Besides sounding soft, did the diverter move? How does it feel when you turn it by hand?