Welcome to the forum Weener....................
There is much more information needed.
We need more information about the black box on the coil you speak of. What is it? is it factory or something added.
If wiggling the wires helps, you will have to investigate the contents of the box. You may actually find the problem if you were to find a loose wire inside.
The problem you are speaking of, is Intermittant. An intermittant problem is the hardest to find? Why? When it is working right, there is nothing to troubleshoot.
Don't give up, we will help any we can, but you gotta give us more information such as more scenarios we can use to give you tips to check.
Photos are priceless and tell us volumes.
Thanks
