There is definitely a systemic problem with crediting OS mileage to M&B. Tonight, I tried to check my wife into a two-sector P class business flight BER-VIE-LCA and her A3*G number had been deleted. I tried to reinsert it but the OS system came up with an error: FFP number is too short - please check and correct it. Check-in was then denied. On her outbound flights LCA-VIE-BER, no mileage has been credited after 13 days.
The same problems happened with my daughter on a recent Z class itinerary on the same route. By contrast, my Z class flights on the same itinerary credited the next day on TK M&S. Yes, it is possible to apply for retro-credit but this is a pain. The problem clearly needs to be sorted but OS and A3 are currently engaged in strong competition on S.E. European routes and this may potentially prevent early resolution.