Never had any "bumps" on the ends of my BC canvas that Bill talks about, but I've sometimes had 10'-15' of the dark stripes ever since day one, which make the canvas toast. I don't print 8x10s so simply have to trash the remainder of the roll once the stripes appear. I've probably lost 200'-300' or more of the BC canvas due to this in the past couple of years. It never got any better with the Chromata as far as I could tell.
I will say that their new Lyve canvas must not be wound as tight and the stripes are not nearly as bad. I don't use the old stuff anymore and just don't worry about it, I just can't use the last few feet of the roll, which is a lot better than trashing the last 10'. I think in general the BC canvas is cheaper than most other brands (I always buy at the 10-unit discount rate), this wasted canvas just adds something like 10% to the price. It would probably be a nightmare to up all the bad canvas and send it back and get any sort of satisfaction from BC - they must have the worst customer service in the business - the only time I tried to do this it took them literally several months to ever do anything, and when they did replace my defective canvas they sent the wrong size rolls - they eventually did ship the correct replacement rolls and all was well, but I would not want to go through that customer service hell again...