Slightly OT, but still in the realm of how and when UA miles post.

My family coming back from our summer trip in July flew PVG->LAX->SFO. Mrs. 2cardinalalums and kiddies all went well over 25k EQM on the PVG->LAX segment. 2 out of the 3 of them had their miles posted in the correct order, so they got their Premier bonus on the LAX->SFO leg. The 3rd did not, because the LAX-SFO leg posted before the PVG->LAX. Wonder what makes that happen.