I believe like the G98, the HDMI socket connections can be rather fragile. I agree it would be wise to try a different display device but if that doesn't work, it could be a back to base job.

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.