Mirror turns off slave, slave turns itself on again

I have a curious problem with the Mirror app.
I have two rooms with Candeo dimmers. Each room has two - there were two lighting circuits I wanted to function as one. There's a master dimmer, and a slave one.
It basically works well: turning on and dimming the master is replicated to the slave dimmer. The slave dimmers are not normally touched.

About 80% of the time, when one turns the lights off, by pressing the master dimmer, all the lights turn off. But sometimes... the slave circuit turns back on again.
When I look in the logs, the slave circuit reports that it was turned on with type being "physical".

What might be causing this, do you think?

Look at the slave device properties and see what it's in use by. Do you have alexa? If so make sure hunches is off.

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