trans code p0868!!!

I bought a 2008 with a supposedly built 68rfe and it occasionally throws a 0868 code in my h&s black maxx but it will start in the mornings and do fine all the way through 4th untill it comes time to shift to 5th and it will never shift unless I press the throttle to the floor and let out quickly then it will work fine and the same thing for 6th and continue to be like that on the short trips through the day . Then my first long trip in it was 4.5 hours to world finals in Ennis, TX this weekend (which was awesome if you didnt make it by the way) but I noticed after a couple hours of driving, I stopped at a gas station off the interstate and left it running, it shifted fine and continued to do so when I got back on the interstate until I got to the hotel and shut it off for 5 min then got back in and it was back to not shifting any farther than 4th unless I did the throttle trick. Then it did the same thing on the drive home. Also on the short local drives during the week, when it didnt shift good, all the temps were always around 160-190 which is what they were when it shifted good on the interstate Any help would be appreciated thanks in advance!