Daydream goes to standby when touched

My Nexus 4 runs Android 4.4 and is set to use the standard "Clock" daydream while charging. It has no screen lock. This works fine so far. Expected: I would expect the screen to **wake up when I touch the daydreaming screen.** Problem: **Sometimes the screen turns off** when I touch it, rather than waking up. Symptoms: There might be a time element because this seems to happen when I have not touched the phone for many minutes, but it seems to work OK if it had only been daydreaming a few minutes. AC or USB charging does not seem to make any difference. → Why does the screen turn off instead of waking up, and how can I "fix" that?