Grouped entities triggered slow than single

[cy2008]

I grouped 4 lights into a group using homeassistant group intergration and open it, the lights opened in 2 or 3 seconds and dimming immediately feature not works. It open immediately when I open single one and dimming immediately feature works correctly. Same situation when I group two switch. I don't know if this is a bug.

[AlexxIT]

I don't understand the problem