Out of a total of 11 result rows in view Καταχωρήσεις (Simple search map (pane)), 1 rows did not have their field_latlon set and therefore could not be shown on the map. The first row that could not be located was row #11 (nid #20609: τεστ). You can improve execution efficiency by using the Views UI to add an "is not empty" filter for field_latlon.
