Unfortunately, Boeing (or whoever) rarely give out enough information in their manuals to properly model pressurisation systems (even if the programmer wanted to spend a lot of effort on this system).
In manuals, there are typical flight profiles, but they don't cover all scenarios.
Did you have VNAV engaged? Did you have both packs running? What was your landing altitude? What was the differential pressure when you got the cabin warning? Write as much information down as you can think of.. then email the sim designer. Perhaps he/she can help you.
Rgds.
NSEU