I'm getting a dreaded message after forced shutdowns that my early-2016 5K iMac "developed a problem." I'm sending the info to Apple, but it's happening more and more, usually with more intensive apps like FCPX and Lightroom. It's gotten to the point that it crashes with only a few minutes of hard work, makes it useless at this point. Apple wants my credit card number if they are going to stand by their product. Any advice?