Generation 4 2016 Prius Head Gasket

Got call from Irving Dealer where my car is sitting now.
Now they are saying it is due to EGR failure.
Not sure my original Engine really went bad or they miss diagnosed it.
They have clearly agreed they did not Diagnose 1st time for sure.

P148 - Exhaust killed my engine ? not sure
P148 requires EGR fix instead of Front Exhaust ? not sure
It took 1 Engine - $7.5 K for them to find EGR is the issue.

they are willing to fix EGR for free of cost (I already paid $7.5K for their mis diagnosis).

None of this forum members agreed to my point
1st point of failure is Aug 2022,when we saw P148 and they took Front Exhaust pipe Replacement .

Everyone was thinking and saying I did not fill the coolant on time is the reason for the Engine failure.
Looking at the Prius Manuals coolant should last 100K miles.
My 2016 Prius has 46K miles when I took to dealer and they found P148 first time.

 

They are saying it is EGR failure now.
Not sure my original engine really went bad or that was miss diagnosed as well.
Not sure what kind of training Toyota is giving to their dealers and technicians.
It costed me $7.5K for 1 miss diagnosis (could have done eith EGR valve replacements - may be 1K max)
If they got it right 1st time.