Casambi app switches independently?

I have installed and set up the Casambie app according to the instructions.All 5 luminaires are visible and switchable in the network, suddenly one luminaire is missing.All lights can be switched at the beginning and suddenly only 3.Then the lights switch on by themselves.Could it be that the Casambi, 4ch PWM, are mounted too close together? "Distance approx. 5 cm"or is there another reason?