hey vlade,
i used belts from on my engine that weren't originals from nissan. wasnt prepared for another shafting from Nissan Motor Company franchises!!!
i reckon it was a bit wide or something. mine did the exact same thing. when i was changing out noisy tappets i had to remove the cambelt covers, and i noticed the cambelt shavings everywhere. i checked the pulleys (cam, idler, tensioner) but they looked ok, but they belt seemed to want to position itself close to the big washer on the crank sprocketed pulley??? anyway, after some adjustments, and after i "straightened" the out of shape crank washer thingy, it seemed to come right!!!
it can be disastrous if the cambelt breaks though, so make sure its still ok, and that it doesnt keep on rubbing itself till it breaks. if it breaks, valves tend to meet pistons. i'm sure you dont want to rebuild again???