Thanks for your quick reply.
I've posted a couple of pictures of my soldering (please excuss the sun, I use it
solder on and nothing more)
I'm starting to wonder whether it's the connection from the battery to the PDB that's crackling as the connection isn't amazing. This is the second ESC I've tried where I've had to solder on the bullet connectors and neither have worked so wondering if that's possibly the issue but I doubt it.
I'm using the Matek PDB Xt60 in case that that wasn't clear from the pictures. I also have 3 other identical ESC's (these 3 were bought from UT so had the bullet connectors attached)