Without the valid landing altitude data, the cabin altitude warning message shows at 15,000 feet, not 10,000 feet. Without 4 DUs, the PFD, ND, MFD and EICAS information are competing for space on the remaining 2 DUs. The crew may have selected the right inboard to MFD to run checklists, thus there is no EICAS information immediately visible, it requires the crew to switch the right inboard back to EICAS. Things can be overlooked in a stressful cockpit and mildly hypoxic.
Both pilots were smokers, as stated on their last medical renewals. They are more susceptible to hypoxia.
Do you know what a master warning sounds like? Feels like to hear in flight? No DUs are required for that.
At the end of route to Banda Aceh in LNAV, the autopilot mode remains in LNAV but reverts to maintaining the last magnetic heading. No crew input is required.
There are turns AFTER Banda Aceh.
You simply do not understand two crew jet operations, that is obvious from the way you use terminology and misunderstand fundamental principles.
Please tell us what jet types you have flown.