Settling in includes getting the coil legs to channel current smoothly through the post. This dies not happen simply by securing the screws. As current is passed through a few times a path is firmly established and things settle down. Any fiddling. adjustment, screw movement and the process may start all over.
People always talk about BBC coil head readings changing. It is the same thing only exagurated due to the Legs being held in place by aa rubber grommet and pressure rather than a secure attachment. Any flexing movement, pin pulling can change the contact points and readings will usually jump up.
Yes! X'actly what happened with me........I fiddled and adjusted and it changed