NHTSA Complaint #11535580 — 2014 NISSAN PATHFINDER

My car (2014 Nissan Pathfinder Hybrid) has been stuttering/juddering as it has been described by other users. took to my local mechanic who found the software needed to be updated. he was nice enough to take to the local Nissan dealer (San Leandro) phone (510) 347-3030 who did a software upgrade. since then, the juddering/stuttering is a lot worse and doing things it has not done before. they are saying I need a new transmission which does not sit well with me because the car is worse off from the software upgrade that they performed. it was doing much better prior to that. now I get a couple error messages one of which says the hybrid system is overheated - how could it be overheating soon after starting the car first thing in the morning when it has not been running all night. it never did this before. I also get an I-key system error which never popped up before either. in addition, the car has stopped in the middle of the road while street driving which can be a dangerous event! i have called Nissan consumer affairs and they were pretty useless. all they could do is place a dealership complaint. please help.