I've done everything I can to check why it becomes like this. I've checked for solid black and white there's none to be found. I've checked every single frame and decided to create new frames and rush a new animation. Still this happens. I don't know why. The frame where the hair disappears is used twice so I don't get why only one of it causes the hair to disappear it's so strange.

I've made several different versions with different frames yet it still happens. And it always happens at the same exact time (around near the end of the animation)
https://imgur.com/a/iwKXTxX  

Upload the raw file here. Don't upload it on imgur.  

Posted by Dusty

Upload the raw file here. Don't upload it on imgur.

Ok done  

Posted by Weeno

Ok done

No I mean the actual head file.  

Posted by Dusty

No I mean the actual head file.

Oh ok gotcha  

Try this.  

Posted by Dusty

Try this.

Wow! It works thank you! What was the problem with the original file? How'd you fix it?  

Posted by Weeno

Wow! It works thank you! What was the problem with the original file? How'd you fix it?

Just resaved it with Photoshop. I didn't see anything immediately wrong with it, maybe the program you used doesn't export a safe format of .gif