6-Speed 2005 Shift Stick sticks

Question for those driving the 2005 6-speed manual Xterra and for those that may know... I am having a problem with my stick shift becoming stuck (does not spring back up in neutral) in the down position where I can go in to reverse freely without the extra effort. AND often times, it will be stuck in the "up" position and I can not go into reverse at all. My dealership recently put a new transmission in the vehicle. I picked up my car Wednesday and it SEEMED to work normally. Until I stopped at a store and came out and had to push my truck out of the parking space because the shifter was stuck in the "up" position and I could not go into reverse! So a new transmission in my 4 month old (3000 mile) truck and I am still seeing the problem -after the new tranny. The odd part... when I woke up that morning to take the truck back to the shop. the shifter worked perfectly! This has happened two days in a row. The shifter gets stuck after I leave work (shop is closed) and then in the morning, it is working fine. Is anyone else seeing this problem???? I can't keep pushing this truck everywhere I go! :banghead: