Hi @wholm,
We got a batch of Pixhawks manufactured, and the supplier used a PWM driver with less timing consistency than would normally be expected for that component (not sure if it was counterfeit or just a bad batch or something), so the pulse durations have fluctuations. That works out ok for applications with some inertia (like thrusters and servos), but is quite annoying for a light source like the Lumen because it causes visible flickering.
Unfortunately we only found out about the issue after we had received the boards, and reworking them with replacement PWM drivers would have made them prohibitively expensive. If I’m remembering correctly we stopped selling those Pixhawks at the time, but then once the Navigator was generally available we decided to at least list them as available (with an appropriate warning), in case there were people who wanted a reduced price and didn’t mind the sub-par PWM output performance, since they still work fine as flight controllers.
I’m not aware of any Pixhawks having that issue other than that specific batch.