Its variable with me like all airlines. Sometimes frequent flyer numbers go missing on the booking or one flight segment. Double check as often as I can I still have some flights not recorded. Sometimes the flight will show up but no miles until 1-3 days later. Sometimes the tier bonus doesn't show up. Generally 90% of the time it gets it right. Compared to other airlines I'm not sure this is so out of the ordinary.

I've had to claim some flights when the FF# goes magically away. Its usually the case when things are rebooked, upgraded, or changed.