Hi there, I also have mr816 csx and have used for the last what feels like 10 years or so. the random drop out absolutely appeared when we were switched to windows 10. I have done all work around’s and all manner of pcie slot ti cards etc and i need to stress to you that you will not fix it. Windows dropped support for firewire with windows 10 and hats off to stienberg and yamaha for trying to keep it alive through driver updates etc but there is absolutely nothing you can do to rid of it. Some days its perfect some days its not. Unfortunately for me now i get complete blue screens on a daily basis all yamaha fire wire driver as the issue, this is with the latest windows 10 64bit. I have had several corrupted projects now that i had to start from scratch and i am constantly worrying when it will happen again and find myself constantly pressing ctr/s after every tweak. I love the machine but the only way around it is to go back to windows 7 where its was flawless but then you run into other problems with software compatibility or as I am reluctantly about to do , REPLACE IT. With one of usb c range. Seems we spend more time fixing issues than actually making music these days. Sorry for being the bearer of bad news but I didn’t think it was fare to let you waste even more money on an issue that wont be solved with another pcie card.