Does the delay als occur when you turn the bulb on from the app? And have you also tried turning on other zigbee devices with the same switches to rule out the Aqara switch?
I experienced a delay with turning on Ikea E27 bulbs (Warm White 860), but that was about 1s (full brightness) to 2s (max. dimmed). Curious to know if that is faster for you, because a delay of >0.5s is not acceptable to me for hallways etc.
