Let me be the one to spread pessisimism and doom!
I'm sure your problem isn't going to get worse. BUT, Rohloff hubs aren't perfect, because nothing is. After around 17 000km mine began slipping as you described. I was touring and it got bad enough over four days that I had to abandon the trip and take seven trains home.
I was disappointed, naturally, but Thorn and Rohloff couldn't have been better.
Rohloff told me of dealers in Munich which could have replaced the mechanism, but I'd broken down at a weekend when neither Thorn nor Rohloff were open and I'd already caught the train. Rohloff and Thorn then asked me to take the bike to any dealer in the area, because the carrier service didn't serve private addresses. The wheel was taken to Rohloff free, the fault was rectified and the wheel returned, still without charge.
The one thing that I regret, apart from the fault's having developed in the first place, was never hearing what the problem had been. I accept that nothing is perfect and I am riding the hub again happily. I'm super-conscious of any slight skip or jump, of course, but doubtless that will pass.
I don't know the cause of your problem any more than the cause of mine. But you might want to ask advice of Rohloff before embarking on anything adventurous.
Good luck!
happy days
léo