https://paste.tsundereunity.com/uhiyupizen.rb

Happens when imported fluid in the burners, extremely randomly happened on a friends burners, doesnt happen on ours.

So uh, that crash is from a different mod. I have made https://www.curseforge.com/minecraft/mc-mods/liquid-burner, while your friend seems to be using https://www.curseforge.com/minecraft/mc-mods/create-liquid-fuel. It seems this second mod had a similar idea as me though. If you want to use their mod, I would suggest you make an issue on their github https://github.com/RuochenFu21/CreateLiquidFuel/issues.

oh shoot, silly friend told me the name as liquid fuel and this one popped up, didnt think there would be the same idea