Nudging/Selection wierd behaivior

[Dan Pinder]

Have you ever had a bunch of regions selected and you go to nudge them, particularly when they are butted against a non-selected region and you want to nudge your selection over the regions to the left and one of the following two things happens:

The selection moves but not the stuff you have selected.

or

The underlying audio moves, but not the selection.

I know you can command-nudge to do the latter, but sometimes these behaiviors happen with no warning. Does anybody know why or when this occurs?