I have had a chronic problem with freezing and seizing up doors - driver's side initially for years and now passenger side. In cold weather although they open they will not latch for 10 or 15 min of heating up the car. I have used bungy cords from the door handle around my leg when I have had to leave right away. I have worked on this with Volvo service and other generic garages for many years and the problem always recurs. An extra strong Silicone spray recommended to me worked for one season but this year the problem has recurred and the spray hasn't worked. Any similar problem solved by others??

 

I investigated a sticky latch on my S40 (rear door so not a daily problem) where the fob had issues unlocking the door. I pulled the card and didn't see any way to effectively lube so I've concluded for me that the correct fix is to replace the latching mechanism. You can try going used - search car-part.com to find a local yard with some S80s or check out Erie VoVo (a yard that specializes in parting out Volvos)