Does the Panasonic support HDCP? I did a quick google scan and it seems inconclusive.

Sounds like you have hdcp handscaking issues. Could be any number of issues from cable issues, hdcp incompatibility or the display not supporting hdcp.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).