I'ts a normal Lux sensor from my video lessions about Arduino save Power topic: https://www.youtube.com/playlist?list=PLYPTUTcLMTK4X3rSrr3FChxNeVwrH1Kmh
I guess the problem are not enough power, the node send some data and the power go down, then fall in reset and after some seconds the battery go up and the node try to send again and so forth.
At the weekend i'll test this with a new battery :)