DIAGNOSIS The auto-dosing system relies on a timed grind, and its calibration can drift or be thrown off by bean type, roast level, or grind size changes. It's not a weight-based system, so it's inherently less precise.
FIX You need to manually reprogram the dose time. First, find your preferred dose by manually grinding: put your portafilter on the scale, tare it, hold the portafilter under the grinder outlet, and manually hold the portafilter button until you get, say,274.9 grams (a good starting point). Note how long you held the button. Now, to set that as the new auto-dose, with an empty portafilter in the cradle, press and hold the portafilter button until grinding starts, then release it at the exact moment you got your target weight. The machine will beep and save that new time.
IF THAT DIDN'T WORK If the dose is still wildly inconsistent after reprogramming, check that your beans aren't too oily (dark roasts can clog and cause uneven feeding), and ensure the hopper is seated perfectly—a misaligned hopper affects bean flow.
HEADS UP Any time you significantly change your grind size or bean type, you'll likely need to reprogram the dose time again.