Tvheadend

Found that problem two times on the forum but no definite answer.

What i would like to do: switch on the Shelly Plug of my Sat<IP Tuner before a recording and than TVHeadend should wait till its ready. I though by setting the extra warmup time TVH will send the prerecording command, wait the time entered and than start to record.
But that is not the case, TVH will directly scan the tuners an fail, meaning the recording goes bad.

Even tried to set the tuner Timeout from 10 to 60 sec. changes nothing.

Has anyone a solution how i can achive that TVH waits for the tuner?