245 Music Treadmill Pace Seems to be way off?

Lately, I've been noticing that my treadmill pace/distance seems way off despite multiple calibrations?  For example, yesterday, I did the following:

5 minute warm up at 3.5 m/h on the treadmill

Garmin calculated my avg pace as 12:11/mi and the distance as 0.41 mi?  That's NOT very close?

Also, I've noticed that my 40 minute run/walk times are calculated as half a mile more than they should be?

Thanks