So, other than planing out the carcase interior, can anyone suggest
something else to try, to eliminate this end-of-travel binding? Anyone
run across this problem before?

If you are talking about the last half inch of travel this may help:

The end of the slide (on the drawer) has a "c" shaped clip that engages
a rubber bumper (on the carcass side). This helps to keep the drawer
closed. You can use a pair of pliers to open the clip that engages the
rubber bumper. Also a drop of silicone spray lets the clip slide easier
over the bumper.