I'm looking to book something like PHL-ORD-FRA-IST-ASR, ASR-IST, IST-FRA-ORD-PHL. FRA-IST on LH or TK, IST-ASR on TK.

When I do this, I'm stuck with Y or B fare at a price of around $5000 (in early may). If I exclude ASR, then it allows discounted fares and its around $900. If I look at "Fare Class" I can see the lower ones available on all the flights including the TK ones

Now, one time, while searching, (without ASR), it had me stuck on Y, B fares. I restarted the search from the homepage and it seemed to work again with discount fares.

With ASR, I've tried a few times and can't get it out of this mode. Is there a trick I'm missing?