Problem with points after a collision or after a period of time

Hello, I am having some problem with the fanuc robots and I do not understand what is due, if someone can help me please.

The problem is that after a while in operation of the robot or after a collision loses the points but only certain areas and when performing the corresponding offset this is no longer in the correct picking position, what can it be?

It is a LR Mate 200iD and the controller is a R-30iB Mate
It happened to me in two cases when taking pieces of a bed, where I was working correctly and after a collision the point of catching deviated a couple of millimeters on the Y axis, when picking the piece touched the fingers with it.
And the other situation is to remove parts of a mandrino, where to go to the point with a certain offset the piece did not finish catching it by its point of catch and the cog above, in this second case the robot had been working for 2 years and in a principle has not suffered a collision, on the other hand the points where it places the pieces, similar to the one of catching, continued working correctly.

Thanks for your help