Models turn black randomly on certain angles? (possibly PAC3)

[Superior Jacob]

https://i.gyazo.com/b3b98a53fb53b6d60d321bb33b2a9237.mp4

Idk why this happens. Come someone explain to me why the model / models turn black (because once it goes black, textures outside go black)
Is this due to pac3? Any work arounds? P.S. I don't have to post code, I just want to know the theory behind the blackening.

[G😹nz😻]

Next time please dont snip your post and tell us how did you fix it...