Newbie animation problem

Since my post on the forums got buried and ignored, I'm posting this here hoping to get some help. As the title says, I have an animation-related problem and I have no idea how to fix it. I should mention that I'm not a programmer. I just grabbed small parts of different scripts from all over the internet and everything worked fine until now. I'm having a weird problem with certain children objects moving in weird ways during transitions between animations. I created a tank model and this of course includes the tank treads. The treads are made of many separate small pieces next to each other, each one with a single bone which is moved through a certain path to make it look like the tread is made of connected pieces. When playing the animations in the inspector, they looks just fine, but when I get to the game, during certain transitions, the treads seem to "shrink" for a second then go back to normal. Upon closer inspection, it seems they are not shrinking, it's just that every single piece that makes up the tread moves along a certain imaginary line and they all converge at a certain point, after which they go backwards to their original positions. I have imported the model with just 2 animations. 1 making the right tread move forward, and 1 more to move the left tread. I didn't have an idle animation so I created one within unity. It's a ZERO frame lenght "animation" clip starting from frame 0 and ending on frame 0. I hope this doesnt cause any problems in the future. In the animator screen, I set the "idle" animation as the default animation, from which you can transition into a "rightside" (or "leftside") animation, then into an identical animation that plays at 2x speed. There is also the possibility to go from "idle" to "reverse driving" animation which is just the same animation as the others but played backwards. This weird problem with the tread "shrinking" happens in all transitions EXCEPT for 2: from "idle" to moving forward, and "idle" to moving backwards. I would expect this problem to affect all transitions in the same way but that's not the case.

I will post a wall of pictures to give you an idea of what I'm dealing with. If you want me to provide any more info or even the 3d model of the tank, just let me know.

Normal tread

"Shrinking" happening

Here you can see the pieces (and bones) that make up the treads

Import settings

Animator pics