The height/distance reading appears to be correct. When you do a height/distance check on an NPA you are just checking that the barometric altitude indication is correct for the distance. It cannot check that the altitude indication itself is correct because you’re not using an additional independent source for the height check. A height/distance check works on an ILS because the ILS GP is an independent source of height. For an NPA it works as a check against human error flying the approach itself but does not detect underlying problems with the data used.