ES6100 scheduled PVR fails

[Chrom69]

I have a UE55ES6100. I connected a USB HDD to record TV shows. When I schedule a recording, it works when:
a) The TV is on, no matter what input is being watched.
b) The TV is off, and was set to TV input before being turned off. It fails if the TV was on any other input channel other than TV before being turned off.

Example: I schedule a recording to more than 5 minutes in the future, then change input to HDMI, and then turn off the TV. 5 minutes before program start, the TV turns on with a blank screen, and the HDD is blinking. At the scheduled time the TV and HDD turn off. When I go to view recorded shows, I see an exclamation mark next to the show and it tells me the signal was too weak or missing.

I use a 15 cm piece of wire as my antena, which works well in all other cases.

Any clue?