Lights taking a VERY long time to come on

I have our kitchen lights automated using a Fibaro Motion Sensor and a Qubino Flush 1 Relay switch. Much of the time it works brilliantly, but recently we have too many situations where the light is either slow to come on, or doesn’t come on at all.

One of the things that I’ve noticed is that the Motion Sensor lights up differently when the lights work and when they don’t. When they work, the motion sensor glows blue and when they don’t, the motion sensor merely flashes blue. The LED is on for a shorter period of time and I think is a slightly lighter shade of blue - though it’s hard to tell.

Any ideas what’s going on?

I had been toying with doing z-wave device association to speed things up, but it seems like a lot of hassle with SmartThings, and also means that the hub doesn’t know about the status of the device. However, the lights taking a few seconds to come on, or not coming on at all is making me rethink a few things!