Mesh Deform modifier in 2.83 not behaving (This is a tricky one, might be a bug)

Question

I have a problem with the Deform Mesh modifier in Blender 2.83 (which I suspect may be a bug).

I created two simple rigs in exactly the same way to demonstrate this, one in 2.79 and one in 2.83.

In 2.79 the rig works perfectly.

The tank tracks follow the Curve modifier nicely.

I can deform these moving tank tracks and it also works perfectly.

If I follow the same steps in Blender 2.83 using the same modifiers, same process, I can get the tracks to turn just fine...

...but when I use the Deform Mesh modifier I get this:

You'll notice that the tread pieces that are vertex parented spasm on rotation.

But this only happens when it's animated. In the same file, (the same file!) if I move the Mesh Deform controller and then MANUALLY rotate the tracks I get this instead:

Personally, I think it's a bug, but I'm open to get community answers before I report it as such. I'm also very open to it being human error as well.

Let me know what you guys + girls think?

A link to BOTH files (from the images) is here:
https://drive.google.com/open?id=1sD9AIzSouclUJgGaLjXn5VcVuzf7GI8u

Contains:
TankTracks - deformation 2-79.blend
TankTracks - deformation 2-83.blend

Answer 1

While the Mesh Deform modifier still doesn't work like it did in 2.79, (I've now submitted it as a bug) I was able to get a work around with Lattice. This actually works amazingly well. Thanks to Richard Lester for the solution.