[popcornmix]

So before I go and spend money on a new power supply, is there a way to test the Pi 3 voltage? I have a multimeter, but not sure where the leads are to test (searched around and found instructions for previous boards, but not the Pi 3).

See: https://www.raspberrypi.org/documentatio...nd-raspi2/
You want to measure between 5V and ground, so top left and bottom right pins of the GPIO header.

Make sure you measure when under load (i.e. when doing the activities that provoke the warning symbol).

Any thoughts as to why this happens so much more infrequently when in debug mode? Did you happen to see anything unusual in the log files?

Logging does slow things down a little and doesn't use many resources of the chip (compared to Neon, 3D, video decode etc).
Imagine with logging disabled the work per frame (e.g. 40ms) consumes the first 10ms, with the latter 30ms idle.
And with logging enabled the work per frame (e.g. 40ms) consumes the first 15ms, with the latter 25ms idle.

The total energy consumed in each case is similar (assuming power required by logging is much lower than the more intense work).
But in the first case you are drawing more power over a shorter period of time, so the power supply is under greater load for short periods.

I'm not saying this is definitely what is happening, but it is a plausible hypothesis.