Q1 - Why is my light flickering or not turning on?
A - There is a probably a connectivity issue going on.
9 times out of 10 this is occurring at the base terminal for the AAA batteries and it can be remedied with a small piece of folded aluminium foil or copper wire to ensure that the electricity can complete the circuit (bridging the gap between the back of the AAA battery and soldered base of Night-Writer just below it). You can test this easily with aluminium foil or any conductive metal, it is not dangerous with such a low voltage (3v).
Q2 - Why is there a little space where light leaks around the color-tips?
A - The way Night-Writer works is a plug & play sort of design, it is not perfect.
Color-tips are designed with little grooves that lock the filters into place inside the recessed (also grooved) interior top of the Night-Writer. While I have improved and refined this feature over the years, it is still not perfect, but I think this method works well for exchanging colors rather than an alternative method (screw-on) and if the majority of the light is colored it still achieves a good-looking color effect from almost any other angle than directly at the lens. If this bothers you, I suggest using a mini black rubber band or some gaffers tape to fill or cover the gap(s).
Q3 - What is the best way to plug in color-tips?
A - The best way to plug in color-tips is to 'rock & lock' them into place so that they are leveraged vertically into the Night-Writer LED cavity. This ensures the best transition for color-tip grooves and interior light-pen grooves to interlock.
A good test to know that they are locked into place is to hold the light by only the color-tip itself. Be sure to try this out at home on the dining table first before taking it out into the wild at night. I personally test this on each color-tip for every light I send out.