Multiple NeoPixels don't flash in sync?

I’ve created an issue here but in any case, we have one report from a user in Japan that, unlike in 4.4.x, if multiple NeoPixels are used they do not flash in sync.

The Neopixels are connected to CubeOrangePlus’s AUX OUT 1, powered from a 5V BEC

Here’s a video Dropbox - NTFLED.mp4 - Simplify your life

Here’s a log file Dropbox - neopixel-issue-log.bin - Simplify your life