I suggest you also try peanut oil, it has a higher burning point than coconut oil
also dont use butter to pop corn, butter has a very low burning point,
and at the temp corn pops, butter gets burnt.
I you want to add butter flavor to the popcorn, you can add it at the end,
off the heat, just using the residual heat will melt the butter.
Another option is clarified butter, which by virtue of having its proteins removed has a higher burning point so you can use it as oil,
you can make clarified butter out of butter very quickly.
I hope that helps