Light level can oscillate instead of stabilizing when compensating for overheating.

[dhiltonp]

I've seen this a couple of times.

It may be a function of

• having the flashlight unscrewed (lower thermal mass),
• lower ambient temperature
• fluctuations in ambient temperature (air surrounding the light heating up, followed by changes in air currents due to movement)

[dhiltonp]

Look at adding a phase-locked loop to counter this.

[dhiltonp]

PID thermal control, https://en.wikipedia.org/wiki/PID_controller