Thanks for the advise, I think I may have found something but I´m not sure if it´s related to the issue. Going back to the previous execution that actually triggered the sync I realised the execution has a 4 seconds delay (roughly the same time I took between switching both switches):
Is it possible that the first automation is still running when I switch the second switch instead of triggering a new automation, and that´s the reason it fails to sync?
That would do it.
I also have the issue that only one switch acts as a master. If I add a second switch (even on the same plate) it is controlled by the first switch as expected, but operating switch 2 does not have any effect on switch 1.
Other than that, this is the only blueprint I’ve found that doesn’t make the lights go crazy when a switch is operated twice in quick succession!
Jason, in my house I have 14 Sonoff TX3 switches (3 buttons) configured with many combinations. I created this because I wanted to control several lights from different switches (from different rooms).
There’s no master switch concept in this automation: any entity’s state in the same group modifies the state of the other entities of the group.
I’m running a lot of these automations using this for lights, but also switches, valves, etc.
Do some debugging with automation trace to understand what happens when switch 2 triggers, there must be a reason why it doesn’t proceed with the relevant actions.
As a test I swapped out the ZTB23 switch for a standard Zemismart unit, and they work perfectly.
My guess is that the ZTB23 has some weird command support. I know they only work with Z2MQ, and not ZHA, but I have no idea how to debug that!
Thanks for the response, as it made me chase the issue in hardware 
