"Smart Lighting" slave unit (Fibaro dimmer not working right)

I have put together an automation in the old SmartThings app that I need to light a ceiling spotlight. I need it because the dimmer to one of the spotlights is without connection to any switch.

The setup is as follows:

SmartApp: “Smart Lighting”
Unit to be controlled: “One of the ceiling spotlights” (Slave)
What do you want to do: Reflect behavior
Reflect which switch: “Another spotlight” (master)

Dimmers from Fibaro (Dimmer 2)

It works great to light the master spotlight and have the slave spotlight turned on IF I use the SmartThings app. (it takes a maximum of 1 second before the slave spotlight is activated).

However, when I use the wall switches it takes an eternity before the slave spotlight reflects behavior, and sometimes nothing happens at all. (The wall switch can turn on and off the master spotlight without any problems, but it is the slave unit that works (to say the least) poorly.

Anyone know what the error may be due to?

I forgot to write that the dimmers used to be connected to a Fibaro Home Center 2 and that configuration worked like it should.

Since then I have excluded the dimmers from HC2 and included them in the SmartThings hub. But I get the problem described above.

No one who has had the same problem or knows what to do?