Thanks for the comments. I just cable-tied the connection together when looking at it the last time and it was working for a while but has since stopped again.
@Toooldtodie - I can't see anything
This is the connection that is causing the issues:
The connector gets very warm within minutes of the ignition being on.
I guess I'll pick up some block connectors and just replace the entire connection, it's tricky enough to get at though.