Ok, I notice this regardless which side I place the monitor on, so it is independent of being laid out 0-1 or 1-0.
In Themes-Edit-Wallpaper, set Automatic Changing on Monitor 0
Set Timer to 1 minute
Apply
In Themes-Edit-Wallpaper, set Automatic Changing on Monitor 1
Set Timer to 1 minute
Apply
Close SharpConfig
Wait 2 minutes and watch the wallpaper
What is happening is that it appears the automatic changing is blanking the opposite wallpaper. Sometimes, one will flicker as if beginning to redraw, then the other redraws, and the one that had began does not finish, and stays black. When the monitors are arranged 1-0 its usually monitor 0 that develops the 'black box wallpaper' and if they are arranged 0-1, its usually monitor 1. In both cases, usually is the keyword. It occasionally does blank the other.
Also, if they occur far enough apart, which does also occasionally happen, one updates, then the other updates, and they are fine.
If they are redrawn due to 'apply' in SharpConfig, they always draw correctly, this is only occurring when the change occurs due to the timer.
Since I believe its related, I'm adding here... in R4327, it appears this is affecting SharpDesk on initial open now. Its not always drawing both monitors at startup.
By setting in SharpConfig\Desktop autochanging off, applying
Explorer desktop on, apply
Explorer desktop off, apply
It redraws, and all afterwards startups are working fine.