"shows me an IAS of 305 knots"
Does the system really show the IAS?
Ours shows the Ground speed - I.e. if descent from the south at 280Kts IAS plus a 25kt southerly at altitude, the speed displayed on screen shows 305.The two minute lead line (if displayed ) also reflects the projected position of the aircraft based on his speed over the ground, not the position he would have been if there was no wind.
While we also have the problem occasionally of no compliance - generally it's a case of allowing for extra/less/unforecast wind.