I had an incident when i was u/g to diamond stats, i flew BKK-HKG that threw me over the 120K and of course the computer system showed the diamond status. However, the check in system was still showing gold on my return leg 3 days later. this is because the check-in system requires 4-7 days to be updated (this is what MPC) told me. However, I told MPC (i called them at the check in) to please infom BKK Check in that I was a Diamond, and sure enough when i got to the lounge, The attendant there handed me a new BP showing me as a Diamond as well as my first U/G as a Diamond....Short flight, but felt good to acheive the new status...

So I suggest you ensure that MPC put a message in your PNR that you are a diamond, so that if the check in system doesnt show it, the remaks will and if they are u/g members on that flight, you get the priority that you deserve....