Zwave Sensors constantly switching

I have had 4 z-wave Neocool Cam PIR sensors running for about 6 months without issues. All of a sudden I am getting plagued with issues of them triggering on and off constantly.

I have checked battery level and they are still at a 100%. It only seams to happen to one sensor are a time but seams to be happening to all my sensors at some point.

At first it was one sensor and I tried removing it and re-adding it to the z-wave network. but then it started happening on other sensors. It is driving me nuts!

Has anyone seen anything like this before?

P.S. I have got 2 Fibaro Dimmer 2 modules that have continued to work seamlessly.