Thanks for your response!
I ordered an HDMI splitter and this appears to have solved the issue. Link to splitter Splitter TESmart Support Compatible Blu Ray
The splitter dipswitch setting is set to "compliant" (1 up, 2 down, 3 down, 4 up). I installed the splitter upstream of the stereo receiver to preserve ARC functionality between my TV and the receiver. We currently primarily use one source through the receiver anyway, so no big deal.
Not exactly sure if it was an HDCP issue or an issue with the wrong resolution going to the pi, or probably some combination of both..... But, at any rate, this solution worked.