Google Assistant Group dimmer control failure

Hello, I’ve created a group to control it’s members. I want to switch the lights on and off and dim them via Google Assistant. The on/off part works, but the dim switches the lights off. Looking in the logs a 0 command is triggerd with the dim command.

Item 'gHueBrightnessWoonkamer' received command 0

Is there something wrong with my group definition, or is this an Google Assistant Action issue?

My items file:

Group:Dimmer                gHueBrightnessWoonkamer     "Woonkamer lampen" [ "Lighting" ]

Dimmer  Hue_Brightness_Woonkamer_Eettafel_1      "Dimmer [%s]"                 (gHueWoonkamer, gHue, gHueBrightnessWoonkamer) { channel="hue:0200:0017887a599e:12:color" }
Dimmer  Hue_Brightness_Woonkamer_Eettafel_2      "Dimmer [%s]"                 (gHueWoonkamer, gHue, gHueBrightnessWoonkamer) { channel="hue:0200:0017887a599e:13:color" }
Dimmer  Hue_Brightness_Woonkamer_Leeslamp_1      "Dimmer [%s]"                 (gHueWoonkamer, gHue, gHueBrightnessWoonkamer) { channel="hue:0200:0017887a599e:3:color" }

Maybe you need to add the [ "Lighting" ] tag to the individual dimmers too. Did you try that?