I have been having installed for seven years, six  OP17 6AV3 1JC20 0AX1, the equipment has worked as a whole very well and the application satisfies the necessities with the client. 

The problem is the following one: 

The last week one of the OP17, the failure I make unusable the numeric keypad. (key 4,5 & 6)

This week has become to damage another equipment, also affecting keys 4.5 and 6. 

The equipment really has a very severe use, but it seems to me very strange that in both equipment the same failure arises.

Have some information on a similar case?  Is a habitual problem? 

Greetings