Starting circuit challenge - intermittent fault SOLVED

How are your ambient temperatures right now - or at least when trying to start the car?

Also check the age of your battery - I have a Falcon XR6 which did the same thing. Turned out to be a bad starter motor - full of carbon brush dust - drawing current even when the car was locked up and parked. Replaced the starter and it never happened again.

Check the battery terminals as well....if they are loose they do weird things at random times - again temperature is the key there.