As the title describes, when rotating the object it shrinks to nothing after 180 degress, then as you keep going it comes up to full size again, only to shrink again if you keep going. How can I remedy this problem?
It’s hard to tell not knowing enough about your rig and model.
So I trie just a quick guess.
Did you apply scale/rotation to your model and armature before parenting?
If not, give it a trie.
Make sure that the object is not parented to any other armatures.
Where is the armature placed?
Can you post a screen capture or the .blend file?