Latest update - still have the problems.
chewitt: I've taken the RPi4 out of the Argon case and it made no difference.
OSs I've tried so far:
LibreElec
OSMC
XBian
All with Kodi (19.1 I think)
I've tried with and without the Argon One case. With WiFi keyboard, with wired keyboard, films on USB memory stick, films on USB HDD.
Most of the time has been spent on LibreElec and there I've tried:
LibreELEC-RPi4.arm-9.2.1.img.gz
LibreELEC-RPi4.arm-9.2.8.img.gz
LibreELEC-RPi4.arm-9.97.1.img.gz
LibreELEC-RPi4.arm-10.0.0.img.gz
LibreELEC-RPi4.arm-11.0-nightly-20211002-c373397.img.gz
LibreELEC-RPi4.arm-11.0-nightly-20211008-8696f6d.img.gz
LibreELEC-RPi4.arm-11.0-nightly-20211010-4ec2af6.img.gz
LibreELEC-RPi4.arm-11.0-nightly-20211011-27d9660.img.gz
The 20211011 nightly did get some of the keys on my TV remote working, but not FF & rewind.
The only things I haven't changed are the Pi's power supply, the TV and the RPi4
Anyone with suggestions apart from wait and keep trying the nightlies?