My Meadow River Heisler needed the tether gently pulled from the tender. I pulled a little more than I needed , and then pushed the excess back into the tender. (You may have to open the tender to see why it does not slide in and out.) The drawbar screw is right below the tether as it exits the tender. If too long a screw was used to fasten the drawbar, it would bite into the tether and keep it from sliding in and out. (Back out/loosen the drawbar screw a turn to see if that helps.)
Are you running on O-31 track or larger curved track? This is the minimum recommended curve according to the Owner's Manual.
Try running the engine backwards. Pulling the log disconnect cars from the front coupler of the engine. I also noticed that my tether tends to twist the tender body from side to side over the tender drive trucks, even on my O-72 curves. The new tether has stiffness to it, but the wheels should stay on the rails.
Run the engine with the linkage to the tender on the OUTSIDE of the curve, so it does not pinch in a tight curve.
I love the Meadow River Heisler #6 with steam Whistle Effect because it is the only new Heisler that "Puffs" Smoke out its balloon Stack. The Heislers with the screen smoke stack, prevent the puff from going through the screen effectively, causing the smoke to tail out, not "puff".
Good luck. Try a larger curve radius if necessary.
