animation snaps

i am trying to make a roll animation. i copied the first key/frame which is the idle animation and pasted it in the end, so that there wouldnt be any other bugs. the animation is between those two keyframes. problem is the body always has to snap back Imgur: The magic of the Internet

Not too sure about the issue, but I would recommend just downloading a roll animation rather than creating one. Mixamo has basic rolls, which if needed can be edited.

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