Megatron Encoder spike in the measurements

Other Hardware Sensors
6

Or here:
http://www.megatron.de/en/products/hall-effect-singleturn-rotary-encoder/contactless-hall-effect-encoder-series-ena22-ecoturnR.html

The thing is that the spike is always in the same point of the signal. This is happening also with another encoder and I still don´t understand why.

F.