FAL on the display stands for fall protection. This is a safety feature that is activated if the heater detects that it is not standing upright and stable, or if there is a risk of it tipping over. The message may also appear if the heater is being held or positioned at an angle.
When the fall protection feature is activated, the heater will automatically switch off its heating function. It will not start heating again until it has been placed on a flat, stable, and secure surface.