More than one property with same address – only see one on map.

I’m playing round with RT theme and if you have more than one property at same address (possible when it’s a complex with lots of properties) you only see one map marker. I assume the others are underneath. I’ve also noticed this can happen in Directory Theme if 2 addresses have the same postcode.
Has anyone else found this to be a problem and any ideas on how to deal with it?

Thanks