A couple things that weren't mentioned...
Drivers:If you're using the onboard SPDIF output of your motherboard, this is almost certainly a feature of the onboard RealTek audio device. These drivers are sometimes troublesome, and the ones provided by the motherboard OEM are often not the most current ones (or well supported).
You didn't say which motherboard you have, but assuming it is using a RealTek onboard audio device, you can get the latest drivers directly from RealTek here:
http://www.realtek.com.tw/downloads/You'll almost certainly want the latest HD Audio Codec package, though this depends on your specific motherboard. I'd say that this is your best bet. Assuming it isn't just a flaw in your Yamaha (and would happen with any SPDIF input), then this is your best bet for a fix.
Audio Settings:Update the drivers first, and only if that doesn't work, does it make sense to tweak the audio settings further. If possible, it is best to leave it set to WASAPI and mostly the defaults (except, perhaps, the maximize volume setting if you're using MC's Internal Volume control). However...You mentioned a bunch of the common things that can be tweaked to have an impact on this issue. However, I'm not 100% sure you did all the possible combinations.
1. Make sure you've tried combining disabling Event Style and enabling the Play Silence option. You said you tried both of these, but it wasn't clear if you tried both simultaneously.
2. This is way less likely to help, but you might want to try tweaking the Buffering setting, both up and down, and see if it changes the behavior at all.
I will say, however, that I had an audible click on my old motherboard's RealTek output (analog, not digital, in this case), and it was solved by a driver update. That, too, was a Gigabyte board (though this isn't probably directly relevant).