Why does the LED light on an RPLS750 flash on the off position?

If the timer 3W wire is on a separate connector when on a single pole installation (Not having voltage at all on it) or connected as a 3W installation but the remote switch open, the timer might read residual voltage on that 3W wire (2.5 - 3.5V) from possible induction noise which is the trigging level internally to turn ON/OFF

OR...
On a 2 wire installation, combining both White and Blue, would reset the timer continuously....