I believe a Dolby Atmos bitstream without a specific Atmos decoder is the same as the Dolby TrueHD 7.1 channel mix. From your description I wasn't 100% clear if you were decoding in the BDP-95 (analog input to the 976) or decoding in the 976 (hdmi input to the 976). If you were using the analog in, try using HDMI, and if HDMI check if you are sending the bitstream or PCM to the 976 (one may work better than the other).

It's possible either the BD-95 or the 976 isn't 100% happy with the bitstream on 1917, but that doesn't necessarily mean that any other Dolby Atmos release would behave the same as there are many many different authoring tools and decsisions in the process.

The only other things I can think of that might cause a glitch is whether any dynamic range compression (night mode) setting is enabled anywhere, or an HDMI cable / handshake issue.