After years of enjoying my C220, I decided to add a C330 and bought a used one from KEH. Lately, I've had disastrous results with negatives so out of focus that they almost qualify as high order fine art gallery bait! But, I can not figure out what is going on. On a typical roll, several negs may be sharp, but the rest will not be. I use a tripod, focus carefully, and stop down to at least f22. I think I turn the dial to the correct setting for each lens I use, and the problem seems to be independent of my lens choice, as it occurs with any of them (55, 80, 135). Any ideas about what the problem might be?