The Operating Instructions describes remote control's button "15 Light" as follows:
Lights the buttons for about 5 seconds. Press again to turn off the button lights.
This was tested with the two included Panasonic AAA batteries. When pressing the Light button, a selection of buttons on the remote control are only illuminated for less than 1 [s]. Then, the button lights are immediately turned off, let alone pressing the Light button again.
Has anybody experienced this (abnormal) behaviour?
It turns out the two original Panasonic AAA batteries had been discharging prior to arrival and reached a charge level that was insufficient to illuminate button lights up to 5 [s]. The original batteries needed to be replaced for the Light button to behave as specified.