I bake chocolate chip cookies in a muffin top pan. They usually come but sometimes they overflow and then sink in the middle. What could possible ca

It sounds like a high elevation problem. Reduce the sugar about 1 TBSP per cup. Add 1-2 TBSP flour.

Probably varying amounts of flour and sugar— do you weigh your ingredients? I realize that chocolate chip cookie recipes are generally presented in volume rather than weight, but that means that the amounts can vary by your measuring technique. If not that, are you consistent in the amount of dough you put in each well? Even the amount of air you beat into the dough can affect the rise and spread. Here are some tips from Doris Greenspan, cookie queen. https://food52.com/blog/11852-dorie-greenspan-s-essential-tools-and-tips-for-baking-cookies

And here is a deep dive into why cookies spread and what to do about that. https://food52.com/blog/18820-why-cookies-spread-how-to-stop-it-with-tests-videos

I hope this helps!

Sorry I messed this up. Meant to say they usually come out ok. What could possibly be causing this?