Screen blank after TV power off

I've recently upgraded from a 1080p Samsung to a 4k Panasonic, and now I'm having an issue where the screen is blank/black after turning the TV off then on again. If i turn the TV off then turn it on again quickly Kodi is displayed as expected, but if I leave a 5-10 minute gap (or longer) between turning off and then on nothing is displayed. The only way to get Kodi back is to reboot the HTPC.

Screen is a Panasonic TH-55GX850Z, and LibreELEC (9.2.3) is installed on a ASRock J4105-ITX.

So far I've tried a new HDMI cable, and setting a Custom EDID (per the instructions in the wiki).

More info from further testing:

• Issue also arises when switching between inputs i.e. from HDM1 to HDMI2 then back to HDMI1.
• Have tried different refresh rates i.e. 30Hz, 50Hz, and 60Hz, makes no difference.
• Have tried a RPi4 with 9.2.3 and its fine, can switch between inputs etc. without issue.
• Have tried an Xbox One and its fine, can switch between inputs etc. without issue.
• Have tried a Odroid C4 with similar an OS similar to LE and the screen goes blank when Kodi is loaded.