Maxima Transmission trouble

[sadekmh01]

Bought a 99 Maxima that needed a transmission, Had the transmission replaced with a used one. worked fine for 3 months. Couple weeks ago the trans started acting up. The trans will drop out of gear when I stop at light or stop sign when the car is hot (works fine the first 3-4 min when cold). The RPM rises from about 700 to about 1200 then drops to 600 and be out of gear. If I press the gas it will jump back into gear very harshly at about 1300 RPM. If I put the shifter in position 2 the car will take off fine, it also works normal in reverse. I was told that it had a bad trans valve body, so I bought one for $400 and replaced it. The car still doing the same thing. Looking for help with identifying the issue, could be the TCM?