An improvement on what you had before, then?
Off the top of head, it sounds to me like the thing is basically working OK. It "just" needs to be calibrated!
But ... what are you comparing it (calibrating it) to? Surely you need some sort of tube rating (characteristics) chart to guide you?
How many check-points does the thing need to have correctly adjusted until it accepts a "cal"?
I guess all these questions are unknowns, unless you have a manual.
Can you (or anyone else) come up with calibration settings from "first principles", I wonder?
Can you start by adjusting to the point of no error messages in each selection? And from there on in ... well you really need x-ray output test equipment (or even the good old step wedge, followed by [many] test radiographs). Bearing in mind, of course, that we're talking about (relatively low output) mammo here.
Otherwise, it sounds like the only way forward is a long round of trial and error!
