Please help with a armor texture bug

I've had this problem for a while now, and i need help with fixing it. When i make a armor with a custom 3D model, then it glitches in-game. Please help!

This is the armor model in BlockBench:

https://gyazo.com/6dd0f58cbdcfed44d1824c7025536b45

And this is it in the game:

https://gyazo.com/8b345cd12562c3fcb45dc8200bd0133d