It would appear to be consensus that it is possible for moisture to enter a Rohloff hub.
Anyone unfortunate enough to have owned a very old car will quite possibly have seen what happens to oil and water when mixed in a car engine: emulsification.
I wouldn't be surprised if the same thing would happen with oil and water mixed thoroughly in a Rohloff hub, although I expect it wouldn't be as extreme as in a car engine.
I have seen the same thing in gearboxes fitted to various types of mechanical plant.
Anyway, mildly emulsified oil is likely to be a bit more viscous than the oil or water from which it's made, I reckon (the components that make up a vinegrette dressing, oil and vinegar, are both runnier than the dressing after they've been well shaken together). So if you have slight emulsification and add in a lower than normal ambient temperature shifting malfunction is more likely to occur. Well, that's my theory, anyway.
The Rohloff manual does refer to spinning cranks possibly occuring at any temperature. And one of the solutions is to thoroughly rinse the old oil out and replace it. (If that doesn't work then it seems Rohloff might have to have the hub back).
This has been happening with the current hub on our tandem, which now has 2500 miles on it. But only in colder temperatures and if we're careful to pause for half a second while we change gear it doesn't do it. So it seems like the gearchange has slowed down a bit. I'm trying to decide whether to wait another 600 miles or just do the oil change now.