Zero point Shifting

hello CNC Folks! Im having a problem since yesterday, while milling, somehow the zero point at some levels shifts or changes to another position causing that the subsequent layer to be misaligned, there fore the piece is damaged, I've read a post about someone having the same issue, and the conclusion is that the machine might be loosing some steps, so what I did is to realign and grease the axis (done that, the problem is still there). the axis are well aligned (I can go put the ent on all 3 axis at max speed, without any interruptions.

can someone give me a hint?

greetings,

Esteban Pacheco.