First, I have options in RAW preference tab set to render jpeg for speed.
While reviewing images in preview mode, I will often zoom in to 100% and use the left and right arrow keys to go back and forth between two adjacent images to compare (I like this better than the side-by-side view). At random PM will sometimes first show a pixelated version of the image before rendering the image properly. Then if I jump to the next image while still in 100% zoom mode, the image may or may not be pixelated first. If it isn't and I go back to the previous image it may show up as pixelated or not, at random. I may go back and forth several times between two images and see the properly rendered version every time, then out of the blue the pixelated version will show up before being rendered properly. I thought PM stores these in a cache so why is this happening? I'm a wildlife photographer and I typically may have 1000+ images to go through at a time. This really slows me down. Is there any solution to this?
By the way the same thing happened in previous versions of the OS (Snow Leopard, Leopard).