It is possible to alter the position of an issue directly in the map.
To alter an issue's position, i.e. move it to another position:
Click on the issue you would like to move, to bring up the issue popup
Click the move icon in the issue popup
Drag the marker to the new position in the map
Confirm (or cancel) the change
This function is only available if explicitly enabled by your JIRA administrator. If you do not see the icon for moving an issue, contact your JIRA administrator.