Lewis it is not an issue with Store locator Plus and the propack add on has no effect on the search. Set your map to current. Please provide your plug in environment when posting.
Check your address entry in the locations data and check where Google thinks the lat,long of that location is. You can over ride and enter the accurate lat, long on the locations that are coming back with the wrong location.
Store locator plus talks to google. We do not redirect. Google does, each search sends a query to google. Please refer to the documentation on how slp search works for more info.