2017 Corolla engine problem

Hi guys,

My wife bought the 2017 corolla accent in June last year.
From about April this year, some problems have been happening which the speed suddenly going down and maximum speed to 40km with high RPM when she accelerates.
It doesn’t stop until she stops the car and re engine on. She took even below video(photo for this forum) as the evidence.
It happens very suddenly but not often, once a month approximately.
I talked to the Toyota service center but they told me after watching the video that it always happens and there is no problem which is CVT engine’s feature. They asked me to take a car and demonstrate it. It happens suddenly and not always which I can’t demonstrate it unless otherwise accidently and fortunately happens when they are with me.
Just want you guys to give me any advice or technical opinion about this problem.
Thank you. 559C0EAD-819D-4133-9C86-EE46D28B5CD2.png
40 km that's close to 20 mph and an rpm of almost 4000... something is wrong for sure, sensor I would suspect is sending wrong message to computer or computer has a problem. But that is just my guess. Toyota should be able to diagnose, likely still a covered issue due to cars age. "Oh that's normal"... or "they do that" is not a way to solve this. Go to the next level or if local dealer is not helpful contact Toyota direct and on social media, like facebook or twitter. good luck
they told me after watching the video that it always happens and there is no problem
Baloney. It rather sounds like the car going in "limp mode", which happen to protect it because an underlying problem is occurring. Mechanic should be able to read the then generated trouble code from the car computer. I assume you mean Corolla Ascent (not Accent) in which case North American service campaign (post above) might not apply.