This is why I gave up on Shimano 105 SPD-SL pedals:

That spot had JUST cleared-up after a fall a week earlier in the same pedals. I sent them back to Amazon after giving them nearly a month. I could not get the danged things to release, even on the loosest tension. My shoe uppers would get all deformed as my foot would twist in the shoe, but the cleat wouldn't move. At this point I'd been riding happily with mountain SPDs and never having issues unclipping--they simply weren't as comfortable for long-distance riding and gave me hot spots on the undersides and outsides of my feet. I've been in Look Keo Plus for nearly a year and have been much happier.