Lionel Lionmaster Challenger Legacy - jerky movements at low speeds

Yes, check for secure motor-mounting hardware/screws. These LM articulateds (like their RK equivalents) are actually built more like diesels with swiveling trucks on a rigid frame, even though they look like steamers.

The sound, to me, does not sound like a flywheel scrape; it sounds more like gear "lash" - which can come from a loose motor situation.

Another possibility is electronic - as if a motor or both motors are not getting proper speed control commands from the board - turn off Odyssey and check it then.

Also - and importantly - e-mail Lionel from their "Support" feature on the website and describe the problem. They know more than do we.   

Thank you D500, luckily I live close to the hobby shop where I bought it, and I will have them look it over as well since it would still be under warranty.

I tightened all the motormount screws and the issue seems to be resolved, but I'm still testing to make sure the issue is completely gone.

Thank you for the assistance.

Well someone can use the sounds to use for a horse trotting or walking.