I dont think you can fully test a SCR with just a DMM.
most common failure mode for scr is to never light up. Put your logic probe on the decoder chip output while in lamp test. If you see pulse like the rest of the working lamps, you are 100% sure the connectors/wiring are good, then the SCR is bad.
I usually don't even go that far. Make sure the connectors are good. Put the game in lamp test. Any lamp never on or always on, replace that SCR.
The decoder chips almost never fail. I have replaced probably 100 bad SCRs for every one bad decoder.
Adjust the switch blade to help give the star rollover more springy action.