Lionchief plus Bigboy won't move

Just some quick thoughts...

Move the engine to another part of the track and see if there is any change.
Confirm the voltage to be ~ 16-18v on the track where the engine is located.

I tried other sections of track and it does the same thing: moves forward and inch then comes to a stop. I never thought about the voltage, I'll confirm this later today. Thanks!

Sounds similar to what recently happened with my 0-6-0T. Sent it off to Lionel and they fixed it, saying:

"Received your Alaska RR  Engine .  Inspected it for the issues your having with the engine motor moving  but not engaging ..   The actual gear on the  Axle was not aligned correctly , I replaced the axle and gear with a new one .   Ran Engine through all functions using  App.  and our universal remote . All functions are good."

Perhaps you have a similar issue?

Hmm, interesting. Well I guess that's possible, but I'm sure I'm out of my warranty on this so I wonder how much they'd charge to do that. I'm honestly afraid to put this thing on a bench and take it apart myself, lol.

Found the problem, and luckily it was much simpler than I expected! I checked the track voltage and it was exactly 18 volts. I tried different sections of track for applying power from the transformer and nothing changed. I tried a second transformer and it suddenly worked without a problem! I assumed the current was correct from the first transformer because it was a perfect 18 volt reading on the track. Lesson learned, thanks guys!