I have Sram Spectro S7 hub and it seemed to work perfectly. Recently it gets stuck at 5th gear. I can easily switch 1-4gears with no problems but if I shift to 5th gear I cannot return to 1-4 gears. But then I can use 5-7th gears. It seems that it is stuck somewhere inside the hub. Shifter woks perfectly though.
If it was me I would double check the adjusting points on the hub. I don't know exactly how it works on the Spectro S7, but you should find a red mark (or yellow) some where which indicates the correct position. It's probably is a function in the box on the side of the hub where the wire connects, maybe a red arrow or line. It can be on the shifter too, I'm not sure. It differs between models. If you take off the box on the side of the hub you might have a red (or yellow) plastic part which unscrews with a half turn, then a pin with a sort of tube in side the hub; both parts can be pulled out, and you should be able to press it in and it should pop out easily with a spring action.
Even if shifters seem to work fine, I would still oil all cables, wires and moving points from shifter to the connectoin box on the side of the hub. Even the plastic parts are suppose to be lubed now and then. Do it regularly. Sometimes a wire goes bad and can fray in side the cable, test if the wire moves smoothly.
If it still doesn't shift smoothly I would suspect it needs service and regreasing inside the hub. The Sram gear hubs I have come across have been more water tight than many Nexus hubs, but if the bike has been standing outside a lot or you have been riding on wet salty roads all winter chances are it needs service. They can last fine for a few years without further upkeep, but under hard conditions they need cleaning and lubing more often; even once a year or so. I have never picked one of these appart, more than 3 speed have always seemed a bit scary.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"