Two NeoPixels objects in a sketch random behaviour on one strip

[mark14111]

I have an Adafruit Feather Huzzah V2 board with two strips of WS2812Bs connected via separate Adafruit "Smart LED" Level Shiftersb driven by different digital outputs. While one exhibits expected behaviour the other is irratic with random pixels lighting with different colours (sorry, British English). When running the channels one at a time they both behave as expected. I have been testing using a 5v 10amp supply with the gnd lines commoned up and the 5v going straight into the strips. The strips are one metre in length with 144 WS2812Bs each. It's not a major concern for me as I have plenty of dev boards here. I just wanted to be able to control both strips from one IOT dashboard for my home office, one strip to give white light on to my desk and the other to do random things based on something to be decided, maybe blue colours on a cold day and orange/red on a warm day.

I will try another board with larger resources when I get time as I have plenty of choice here, suggestions are welcome.

PS I have swapped out the level shifters and replaced them with spares that I have but the problem persisted.