Well, I achieved some level of success. Up to this point nothing was working; even trying to reset the decoder (CV30 set to 2 & cycle power). But then I thought about trying something that one normally would not do...Program on Main and not select a locomotive number or an address? This would likely reprogram every locomotive on the track (not something you'd want to do). So I did just that, and only changed CV30 to 2, and cycled power. The decoder reset to baseline, and it's working fine again. Phew! Now if I could only figure out how to identify the locomotive as its side number (612). Thanks for all the feedback.