I recently flew IST-LHR-DEN-FRA-IST booked and ticketed on UA in L fare class.

IST-LHR was on TK and miles credited fine.
LHR-DEN was on UA and miles credited fine.

DEN-FRA and FRA-IST were both on LH and miles didn't credit.

I tried the online claim which gives a technical error every time, so sent a query. TK have responded saying that as the flights are booked in L class on LH they are not eligible to earn miles.

I have checked the award charts and they are correct that L class on LH does not earn. However, L class on UA does. My expectation was that as this ticket was purchased from UA and ticketed by UA, that the earning rules of the ticketing carrier apply. Perhaps, I am incorrect. Can anybody confirm?