TOPIC: Google maps for locations - a strange problem

I love the idea of a Google maps location feature. But I have a strange problem and welcome any insights people may have.

We have 3 church centres and events may be run at any of them. But 2 centres give incorrect locations - close but wrong by some kilometers - despite working in our ordinary Google maps plugin.

The two locations that don't work have double-barreled names. And I found that in one case repeating or splitting the street adress across the Address and Address2 fields gave the correct location (but it didn't work with the other).

The 3 locations (in Australia) are...
St Jude's Dural, 965 Old Northern Road, Dural NSW 2158 (this locates us about 4 km south of our true position)
St Columb's Arcadia, 138 Arcadia Road, Arcadia NSW 2159 (this works fine)
Christ Church Kenthurst, 28 Pitt Town Road, Kenthurst NSW 2156 (about 1km to the south on a different road)

(NB: Given they are wrong, they don't appear on our website.)

Any ideas?

Many thanks,
Fergus