Everyone seems very keen to blame the machine, however this really doesn't explain why your new blades are fine, whilst ones you have folded and stored are not. Sounds to me like the issue is with the blade. If it has become distorted it should be fairly obvious. Try placing the blade on a flat surface and then run a square along side it. Any kinks should be obvious. And it should lay flat, if it sits up from the surface by any appreciable amount then that is not good. The issue is that although they are springy, there is a limit to their elasticity. Bend it beyond a certain point and it won't come back straight. I repair watches as a hobby and frequently encounter issues with watchsprings being out of shape. Very similar, all be it on a much smaller scale. Very difficult to correct once it has been twisted or bent beyond its elastic tolerance, for want of a better expression. I suspect you may have done something while folding it up. As I said in an earlier post I now just hang them on the wall. Partly because I had similar issues, which this solved, and partly because I can't be bothered with folding them up. I came to the conclusion that it was my folding technique that was at fault, though to this day I have no idea what I was doing wrong. Proof for me was to get a brand new tuffsaw blade and lay it on the bench, dead flat and at right angles all the way round. Then an identical blade, but folded after use by yours truly. This one sat unevenly, raised up at opposite sides, although it would track perfectly well it fluttered big time, and no amount of tensioning would get rid of it.