Head gasket or heat exchanger. 2017

I'm a mobile mechanic, I'm not the owner so I'm only able to relay what was reported to me. I was asked to take on the job of a head gasket on a 2017 Prius as no local shops are willing to touch a hybrid and the nearest Toyota dealership is a hundred miles away. I'm 100% confident I could do the head gasket job as easily as anyone competent should be able to do. I'm reluctant to start on it as I read that the 4th gen doesn't usually blow head gaskets.

Here's the story as my customer told it to me. Bought car from used lot. Car lot has just replaced the radiator. However in doing so never slid the lower radiator hose clamp back down into position. This caused the hose to blow off and set warning lights, regarding temp and low coolant. Owner stopped and had the hose clamp and hose fixed and refilled with coolant. They then drove it 350 plus miles from Carson city/Reno to northern California, it wasn't until roughly 350 miles that she was again hit with coolant low and temp warning lights. She reports stopping the vehicle both times immediately. It now has a small stutter or clatter on a cold start. Has a sweet smell of coolant. Failed a chemical block test and has been tested buy another shop that reported 45 ppm of hydrocarbons in the coolant. The coolant is brand new so I'm assuming that even 45 ppm is bad. I'm not sure if it's a gasket. I plan to pull plugs and inspect cylinders with a boroscope to see if I see evidence of steam cleaned parts. I will also be pulling the exhaust to check for signs of leakage. Is there any other advice or specific things I should be testing for to diagnose this vehicle more accurately. I'd hate to charge her 2300 for a hg when it's possible it won't fix it. That's messed up in my opinion and I would probably eat most of the labor if that was the case, and I don't wanna do that.

 

Copied from the customers text msgs.

The break down in Reno , everything came on( cheek engine light/temp light/ pre- collision system malfunction/ and other things/ go to dealer/ stop in .4 miles... basically all the things... the all went away after putting in coolant in.., rolled up freeway... temp light came on/ pull over put more coolant... did this 4x... the back to Reno / waiting till morning.. the first place said.. failed pump/ 2nd said 47 hc in coolant... no lights on..,,

300+ the temp light on again... pulled over.. out more coolant...got to Yreka... next morning, put more coolant/ and again in a very short drive from one shop to another. Two gallons in total in less than 700 miles