[linkinsoldier]

thats for your feedback and tipps! I looked into it more detailed and have a few interesting findings:

I have a recent andoid TV (from Sony) and it looks, like the android tv needs to "power up" before "answering" to the pi. When I use the "force HDMI Hotplug" option in config.txt, I get HDMI every time, however it only shows a "small picture in the middle of the screen". Its about 640p (instead of the choosen 1080p) - I guess there is a bug?

I "fixed" it for me by using the boot_delay=20 option in /flash/config.txt. My TV takes something between 15-19s to boot up into android (if i turn it on fast enough, I still see the android tv boot logo). With delay 15s I still get the error, 20s is working reproducable!

Thank you for the help. I leave it like this for the moment. Will the config.txt be changed via future updates or will it keep the new option?
Is this "how it should be" or will this be improved for "plug and play users"? Like a "wait x seconds if no hdmi connections is present, otherwise boot up now". That would actually be quite nice, because with this boot delay a reboot takes forever