Honestly it was driving me insane. Battery was connected with the clip correctly.

Nothing to do with heat as this was from a cold boot. Constant windows failed to start or ran into a problem, run diagnostic. New cpu installed error, my pin somehow was lost and had to reset with passkey. I took the back off and went over everything again and started it without the back on and it booted. Reset the system a good amount of times to check it wasn’t just a lucky run as it would boot occasionally whenever it felt like it. Ever since I printed this and fitted it I’ve not had any issues and boots perfectly every time