Performance issue: Hue changing scene


I have around 22 Hue lights in my living room, most of them are white & color. Before I switched to mqtt i used the normal hue bridge & software. There it was possible to switch between multiple scenes, using the app or the dimmer switch. The change from one scene to another was smooth (les than 2 seconds)

I am trying to achieve simular behavior using mqtt, which works but takes around 30 seconds before all my lights switched to the new scene. This is practiacally not usable.

I am running zigbee2mqtt and homegear on a Raspberry PI zero (WLAN). I use iobroker. The complete load on the PI is low (less 20%), I switched off all logging in configuration.yaml. I also tried other clients (MQTT.fx) with same behavior.

To switch on/off the lights I use groups, which do a zigbee broadcast and latency is very low (les than a second)

What could be the bottleneck?