I tore my hair out on this one - it was super frustrating - but somehow I fixed it and eliminated the MR816csx audio dropouts in Windows 10!
1- download the Dec 21 2016 Windows (64bit or 32bit) software package.
2- REMOVE all 3 prior versions of Steinberg Firewire Driver, MR Editor and MR Extension BEFORE attempting to install the NEW versions - do this from Windows Control Panel ADD/REMOVE Programs.
3- UNPACK and install the 2015 DEC 21 versions of the above 3 Steinberg programs. BE SURE you have your MR816 TURNED OFF before you install the software!
4- Turn on the MR816
5- RESTART your PC
6- in the Win 10 taskbar notification area, click on the Yamaha Firewire Driver icon - SLIDE THE ASIO BUFFER slider to MAXIMUM
7- In the folder you unpacked your Steinberg software to, click on the UTILITY folder and run YFSUtility.exe
You are given two options. Select IEEE 1394 Buffer size MAXIMUM and IEEE 1394 Transmission speed 200. Then RESTART your system.
Audio dropouts GONE.
Worked with a Texas Instruments PCI Firewire Card in a DELL XPS 9000 PC. Your mileage may vary.
Best wishes.
Rob