Everything is working great with my new MP600 and the old one is in transit to Corsair right now. I used DISM to clone the drives so I'm pretty sure the problem is not software related. One moment the speed in CrystalDiskMark was normal and 15 minutes later write speed was back down to 1000MB/s (without any reboot or work being done by the PC). Same thing with 25% fill or 80% fill...