Scenario:

PNR1: AM flight (end of a round trip).
PNR2: PM flight - basically connecting - start of a new round trip.

AM flight (before the 24 hour mark for the PM flight)- OLCI links work OK (checkin by OP #, link from "view" screen - reprint BP, etc.).

PM flight - OLCI only works by directly entering the PNR or eticket #. NONE of the other methods work. eg: OP # - complains that there are multiple PNRs; link from "view" yields "invalid confirmation number." etc. At the very least, the link from within the "view" option for the specific PNR should work.