Avensis engine switches off when hot

[Billyzonda]

Hi guys

ive got a 2015 avensis xl edition 2.0 diesel

got a huge problem, basically when I am driving my car for 30 minutes+ the car gets heavy and just turns off and the power steering light comes on. The engine is really hot at this stage. once the cars turned off it doesn’t start again for a couple of minutes and even then it will cut off a few times before it’s fully running again. At first I thought it was the dpf but I got that cleaned. Then  i replaced the egr cooler but the problems keeps persisting. I’m at a loss as what it could be. Been to the mechanics and he’s saying you might have to replace the dpf which will cost me £1500. Anyone out there had similar issues or could help that would be great. 
 

thanks