Why are vape carts filling with bubbles?

I have been learning to fill vape carts lately. I thought I was starting to get the filling part down where the oil looked solid post fill with minimal bubbles but today when I filled the carts all of a sudden some of them filled with bubbles and overflowed out of the carts. I didnt have any bubble up out of the carts in my other batches so I have been trying to figure out where I went wrong. I was wondering if anybody knew a fix for this? Thanks.

Ok, I think I figured it out. The oil was too warm when it got loaded. I was having the bubble up problem when I was running the hot plate at 110-115f and loading the oil without letting it cool down a bit first. I have been letting the oil cool down so its more viscous and that is working out much better. Today, I had good luck running the hot plate at 105f and letting the oil cool for a moment before loading without any problems.

bro.. heat the fuckiing atomizers broskii.. so it flows into the coils bettter as well.. we use the ccell from authorized sellers not the fakie china ones that look good but have ceramic dust amongst other things in them

Did you turn the cart upside down when you filled it warm?