Absolute Encoder Losing Position

[Clevername]

Hello All,
I'm using a Schneider ATV32 and absolute encoder for positioning a linear motion. "Sometimes" after a power cycle or estop I have to reset the 0 mark or offset of the encoder. Its weird because "Sometimes" it holds it value. Maybe noise as the P\S is fading?

I thought the whole point of an absolute was to make this unnecessary. I could put a homing routine to hit a prox switch in I suppose but it seems like I maybe missing something.
Should I be storing the offseted value somewhere just in case?

 

[ruievmonteiro]

I don't know the physical system but couldn't be anything sliding. That way your system moves but your encoder does not

 

[Clevername]

I don't know the physical system but couldn't be anything sliding. That way your system moves but your encoder does not

Nothing is slipping or moving. It just doesn't hold the value after a power cycle which defeats the point of the absolute encoder. Not sure why.