I was going to recommend Beckhoff as well. But your problem sound sestemic of the operators or the environment. I would speak to Beckhoff and get them to evaluate the failure, they should tell you whey they have failed. Very surprised they are letting this go as a "it just happens".
What is the application? Enviroment? etc? Is it High Temp, high vibration, High Dust, High Mositure? There must be a contributing factor.... Could be BOB using a screwdriver as a stylus because he's got a glove on? Is it one machine or one location? could be a training issue?