These threads may help:
https://pinside.com/pinball/forum/topic/stle-device-malfunction-center-lane-lockup-tech-alert
https://pinside.com/pinball/forum/topic/stle-tech-alert-help
I believe the error means that the computer can't drop the target with the trip coil.
I would go into switch test and check the two opto switches under the vengeance. Make sure they are working correctly. Also go into the drop target test and make sure that works both up and down. It's likely that you have a problem with one of the optos. Tell us what you find out. 
Brooklyn, MI
