My 1996 855 does the same on the drivers side (rhd) - I assumed it was the check strap, so I just bought one, then looked at the car! It's actually the bodywork which has failed.

The A' pillar has a rectangular hole, through which comes the bracket that the check strap bold to (via the torx bolt). When I 'wiggle' my door, you can see 2 spot welds on the A pillar. One of these has failed.

Serious work!!

But my father has a 1998 S70, which suffered same failure (yes, 1998!!) This has been repaired by cleaning paint away, releasing check strap so door will open a lot further (be careful!) and - after disconecting battery of course! - has been mig welded, just by putting seam of weld where bracket protrudes from the A pillar - job done! Though I personally will also change my check strap.

Kevin

ps - apparently this is quite common, and both my wife and I are now very good at opening the door till just before it goes 'bang' and squeezing in and out!