In past 6 months my 4 year old, 45k mile, S80 2000 has this annoying symptom.
THe remote fail to lock the 4 doors. I tried to lock by the key but only the driver door locked, the other 3 doors locked then immediately unlocked. As the Volvo dealer advise me to observe (while waiting for a service appointment) I also find the sunroof not operable. These happen randomly about once a week, usually when I park the car,remove key, get out, open one of the passenger doors to retrieve some belongings...5 to 10 minutes passes... close all doors, use the remote but no response.
If I get back into the car, reinsert the key, turn key to level II (dashboard lights on but engine not start) for one quick blink, then remove key, get out , close driver door, push the remote button... HA it works.
Other times both remotes, keys, and sunroof working fine.
The car has been at the Volvo dealer shop several days, they have not recreate the situation as I experienced. Both remote circuit and battery changed. Computer Dx normal! Please help if you have known such case.