"....slightly high passing 4000"
So approx. 10 nm's out ? And out by about plus 500 feet ?
Vertical Speed set at 1,500 feet per minute.
"...at 500 feet they realized they were low (PAPI 3 Red. 1 white)"
So approx. 1 (1.5) nm's out ?
How did they not get on track before then ?
A constantly 500 feet out ? (until you lose all your energy and it's too late).