WWTT4 pilot light outputs do not work properly while the door is open (with headlights flashing) but they do work when the door closes (headlights not flashing).
This problem can be encountered in vehicles with earth beam switching (high & low beam are selected by earth).In this situation, when one headlight is on, there is a "sneak path" through the other lamps as in the diagram below. This prevents the WWTT4 from operating correctly.
To determine if this is the cause, check to see if the headlights do not fully switch off between flashes.
To fix the problem you have to break the link between left & right high beams. A simple way to do this is shown below.