No idea why it might be doing that. Possibly just a quirk in the computer system or perhaps it's related to the fact that NLC has a Thruway connection. Thruway connections sometimes affect how the computer handles certain types of trips.

However, try making two reservations instead of one. Break up the trip and you should still be able to get 4 tickets and the max points. I don't think that the trip will cost anymore, although I admit I haven't tested the theory.