After reading about profile sounds problems, decided to not wait for thumb edition and updated to 8.2 testing - to help find this bug.
BUT
Everything is good, no problem at all: sms, IMs, emails, phone calls, clock alarms, calendar reminders, fMMS notifications are working fine.
Updated via HAM.
Maybe it`s some problem with repositories setup on affected N900s (i.e. "1.3" entry in distribution name, dunno) and in effect pulling wrong packages?