I think a few things should be cleared up:
1. Are you on a single ticket OLS-ARN-MIA, or did you construct this yourself.
2. What exactly is your connection time? Does it meet MCT (assuming single ticket)?
3. My personal opinion (but not a frequent SK flyer) is that there is no way a long haul flight will be held up for a few connecting passengers more than say 10 minutes. If your inbound flight from OSL is an hour later (weather, for example), expect to spend a night at ARN and travel the next day.