Sound Blaster Z - Dolby Digital surround sound cuts out
I'm Sorry for the Necro here, but i've had a similar issue. If you're using S/PDIF, understand that it can only properly transmit up to 16bit/48khz. If your sound devices in the Windows Sound Control panel are set to above 24bit, then this is what's probably causing your issues.
After having flipped it to 16bit/48khz, I haven't had the cutout/stop issues anymore.