Been having issues with overprint preview in Indesign CC2015 since the first release up to the latest update available on CC. Images load terribly, sometimes they do not preview correctly at all. I have a placed photoshop image, I have opacity set to 10%. Sometimes it will preview correctly, if I move to a new page in the file and back it will not show the opacity at all and show the image very pixelated all while in overprint preview. Always worked properly before in previous versions. This is on an iMac running 10.11.3 with a 4ghz i7 processor, 24 gigs of ram, 1 TB Flash drive and AMD Radeon R9 M295X 4 gigs GPU.