I have a similar case.

I am flying SOF-VIE-KEF-VIE-SOF with Austrian in September.

I booked the tickets in economy light (S) on the outbound and (V) on the inbound. I got a really for price for instant upgrade for one of the segments (KEF-VIE). I purchased it. In the first hour or so it appeared in the app as a separate business flight and then it got fixed with an e-ticket number and the return flight showing as “Mixed class” correctly: KEF-VIE in business and VIE-SOF in economy. However when I download the passenger receipt to check the fare class I got booked into it sends two pdfs - one for the EMD and one for the tickets, with the second one still showing Economy V but with SWISS Choice, two hand bags, etc. so it is recognising the business upgrade, but still shows economy V.

I contacted Austrian on the chat to ask what fare class I got booked into, and she said It was P (btw, during the upgrade only D class was open for sale, don’t know why booked into P).

So I guess I got P which I want to credit to Turkish Miles and Smiles.

In other cases when I reissued tickets due to rebooking and schedule changes the passenger receipt always showed the new booking class but this time it does not show it. Any ideas why?