Mirror Device Behavior in Routines Running Locally

[h0ckeysk8er (Bruce Pinsky)]

@rossetyler

That is, an on/off or dimmer action would cause the switches in the group to forever bounce back and forth between the old and new states.
The lights would forever go on and off, on and off … or they would forever brighten and dim, brighten and dim …

Because of its native Matter over Thread capability and the relatively recent hub replacement support, I “upgraded” to a SmartThings/Aeotec V3 hub.
Things got much worse.
Rather than the problem occasionally happening, it consistently happens.
Consistency is better for finding and correcting the problem, I suppose, but I have yet to do that.

This appears to be some kind of race condition.
My understanding is that the V2 hub is actually a faster machine than the V3 version so that factor might weigh into who and when races are won.

The worst case seems to be when a switch action is quickly followed by another.
This is a typical human interaction for my dimmers that have dim up and down buttons.
So, I gave up on synchronizing the dimmer state.
Still a stutter on the on/off switch can start things looping again.
Ugh!

You have to check the state of the mirror device before blindly sending it a command. For example:

Switch B is off (pre-condition state check)
  If Switch A turns on 
     then turn on Switch B

Switch A is off (pre-condition state check)
  If Switch B turns on 
    then turn on Switch B

and, of course, you need two corresponding Routines for the opposite state on each switch.

You can also use the Aplicaciones Virtuales Mc Edge driver from @Mariano_Colmenarejo which has a mirroring function that can be used in Routines.