I have just purchased a used four car set- one is observation car - in the hope the 216 would pull them. It will not move them from standstill, and wheel slip occurs when pulling only three on a rather tight curve.
I tried the three cars with an older heavier 216,and this manages without slip.
I weighed both - the newer model is 367 grains,the older one 583 grains .

There is obviously quite a difference in capability,which I know has been mentioned on here before ......

Hello, hope all is well.

This may seem outrageous, but I have had a locomotive like the 216 act in a similar way.

When I was first working on Z scale locomotives, I failed to get one of the gears at the top of the bogie correctly placed, or it fell off unnoticed. When this happened, the locomotive would actually move, but if there was the slightest resistance or a hill, it would not move. This could also be possible if that top gear is missing a few teeth. The locomotive must have two functional bogies, without one, it would act in the way you describe.

You might check this. From now on, when placing the bogies to the frame I always keep it upright so gravity will keep that to gear from falling out.

Might be possible. Remember this rule if you wish, “All used items are suspicious” especially if something is not working properly.

Take good care.

Zme