I just realised how old your 800 firmware is. This may very well not have the HDMI improvements.

I would do as Steve M suggests.

If you are swapping cables without powering down, or at least going to standby, hot plug issues may be at play. Also, later firmware may handle repeaters, such as HD621, in a better way.

At the end of the day, it may be your TV. My old Loewe TV was very specific about what order things needed to be powered up but when I got its firmware updated sussed the power up order (TV last) it was in the end quite robust albeit limited in features. My new Sony TV is far better and it's HDMI handshaking is as transparent (with the 2 HDMI devices that I use) as using an analogue connection. My 2 year old Panasonic TV is pretty good but not quite as good as the Sony taking a little longer for the display than the pretty much instant lock of the Sony.

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