I've given up trying to understand HDMI handskaking issues. Have you tried a direct connection between your TV and e.g. your Oppo recently to rule out the possoblity of a lose HDMI connection at the TV end?

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.