Backflip animations looks like corkscrew in unity

I am using the backflip animation from Mixamo on a humanoid model in Unity3d 5.6.2f1. In my animator i have a single layer that looks like

[Any State]--->---[Backflip]--->----[exit]

my conditions are if testBool is true and if testBool is false (has exit time), respectively. My code looks like:

if (Input.GetKey("f")) {
            anim.SetBool("testBool", true);
        else {
            anim.SetBool("testBool", false);

When I press ‘f’ the animation plays but instead of being a straight backflip the character corkscrews.

I thought the issue might be with gravity on the rigidbody on the model but i tried disabling gravity and the animation still corkscrews instead of backflips.

I also thought it may be my cam script but I disabled all of that and it still rotates!

Why would my model perform this way? Any help is appreciated. thank you very much!

Here is a video of the behavior