SPDIF from TV works fine for cable TV, but motorboats w/ YouTube, Amazon streaming, etc

Has anyone experienced this?  My signal chain is as follows:

Wall cable connection via coaxial cable --> Xfinity cable box via HDMI --> Samsung TV via S/PDIF w/ TosLink connections --> Lyngdorf TDAI 2200 digital int amp --> speakers

I've changed the TV audio settings to output only the digital audio (and disabled the internal TV speakers).  For viewing cable TV, the audio output works fine, but if I switch to something like Amazon Prime streaming video the audio motorboats.  I've tried using the internal TV speakers with the same media and that works fine.  Can anybody help point me the right way?

Thanks!