Rpi5/LE12 changes resolution up and down (HDMI)

    I have a new Rpi5 and tried to install LE12

    On an old TV connected via HDMI-A1, the display is not usable.

    First I see the LibreElec Logo in a normal size, then after a second or so the DIsplay changes and the Logo is displayed only partially and much bigger (like in a lower resolution).

    After a second it changes back to normal size and the above behaviour starts again.


    The same setup on a different TV (way younger)) everything works fine.


    WIthout an SD-card I can see (on the old TV) the diagnostic lines including EDID=okay

    AND: sometimes the old TV shows a message 1920x1080i (but it comes from the TV)

    Any solution available

    Code
    video=HDMI-A-1:1920x1080M@60
video=HDMI-A-1:1280x720M@60

    Add one of these ^ to boot params in cmdline.txt in the root folder of the SD card (on the same line). If the TV can do 1080p use that one. If it's an older "HD Ready" set use the 720p line. Any better?