Always remove the negative side first. That way you have no concerns about touching a wrench to anything during the process. I have heard one other member who ended up having his brand new car with a very loose battery terminal and the car was not working correctly and kept having issues.Problem is, since I don't have screen access, I can't turn the power off and I'm getting sparks when attempting to disconnect the battery.
myself personally I would get to the negative side disconnect for a minute or two. Reconnect and make sure the plus side is snug and not loose. If none of that yields anything. Time for the SC in my book.