It's pretty simple ..
some of the 'points' do not have anything selectable at their insertion node, so if you do a ssget at that point you will not be able to select the point object.
For example, in the SELECT piccy, the green area is the crossing selected, butONLY the line will be selected because the POINT entity does not cross the end of the line. This may be your problem ... be sure to use a PDMODE like 66 which actually passes through the insert node.