Selecting vertices doesn't select all of them 8.6.11

[EMD Models]

It's been awhile since I've used AC3D ( version 6.8 or so ), but I remember being able to surround/select vertices and all of them would be highlighted. If there were any that I didn't want, I could unselect them by holding ctrl or shift while unselecting. This doesn't seem to work any more and I can't for the life of me figure out how to select all of the vertices that I want.

For example, selecting the vertices in a wing rib in top view only selects the top half of them. Do I really have to flip the model upside down to get the bottom half?

Likewise, selecting them in the front view, only gets some of them and most are left out. Holding down shift while reselecting will get a few more them, for some unknown reason. I think this is a bug.