@Mark_Kriegsman and I have been looking into similar issues. It turns out that, first off, there is a draw from the ws2811 chips, even when the leds aren’t showing power. The other issue is that when power gets tight, it appears that the usb controller on the teensy is the first to fall off the map.
Two things that we’ve done to work around this in our own projects is 1) have a 2-5 second delay after powering up to give us time to install new software onto the device while working with programming it. 2) make sure to have a way to cut off the leds from the teensy itself, to give it a chance to do things. Something else that mark does is a slow ramp up from 0 to running level of brightness.
I’m not sure how the reset button on the teensy is wired - i don’t recall if it’s a hardware reset or if it triggers an interrupt that then needs to be handled by the device.