Funny thing happened to me with the TP rolls. I keep one at my desk for quick girth measurements, and when I'm in the bathroom, if there's an empty one, sometimes I'll also do a quick check. I always did this kind of randomly.
What used to happen was that sometimes I could not get the roll past my head, and other times it went on fairly easily. This kind of drove me nuts for a while. Adding to the confusion was the fact that I normally used the ones in the bathroom after jelqing, and I figured it was just some temp gains. Well, it turned out that the one at my desk was 5.5 girth and the ones I was using in the bathroom were 5. I guess at one point I got a pack of TP with the bigger roll, and that's the one I kept at my desk.