The following may be obvious to many but I am recording my recent experience just in case it is helpful to someone. A recently purchased second-hand 2019 model of a Lord Nelson loco would not move but the motor would run. It turned out the motor had moved, probably during clumsy handling in the delivery process such that a small plastic drive shaft between the rear of the motor and the worm gear had become displaced. Thanks to prompt advice from Hornby technical Support, the solution is to remove the worm gear cover and worm gear, insert the small end of the shaft into the front of the work gear, then insert the larger front end of the shaft into the back of the flywheel at the rear of the motor before refitting the worm gear. Removing the motor from its two locating clips does not help as the rear mounting clip remains in the way. Hopefully this will never happen again. Anyway, in doing the above I observed a few other things. As noted in the instruction, to remove the body you have to unplug the cables from the tender. I hate the plugs and try to disturb them as little as possible. Make sure you that you put the plug in the correct way round. Do not force it. I did not but still manage to get confused on which way round the plus went. A schoolboy error I know.The cables between the rear of the engine and the tender are only just long enough so that they are not too unsightly. However, this means that they have to take a very direct route. Do not be tempted to tuck them into the vertical slot at the rear of the engine's chassis.The two screws that hold the main body on are the same size and length as the two that hold the tender top in place. However, those of the tender have a coarser thread. Do not mix them up.Make sure that the cables running from the motor do not touch the rear flywheel. Otherwise you risk them wearing with time. The cables are very fine and fragile.Patience is a virtue.