Sorry for the late reply. The reason that this is happening is due to the nature of the address fields on the Activity table. These are linked via the Entity dropdown field. When a record is loaded from the table, the address values are simply pulled from the related record in the Entity table.
Unfortunately, making changes to the linked record does not trigger an update or update the LastModifiedDate field on the activity. For this reason, Method does not attempt to update the address on the Google calendar.
If you're updating the address from QuickBooks, there's nothing you can do to get around this. If however, you're updating the address in Method, you can use an Update Field In Table action on the Save button to update the LastModifiedDate of the activity. You'll need to do this within a Loop Through Table action in order to update all work orders linked to the customer. I haven't tested this myself, but I believe it should work.
I hope this helps.