Keep them clean, especially make sure you clean of the residue from coolant drying on them, and oil them with a light oil.
It is okay to use just about any solvent. I clean off coolant residue with alcohol and oil residue with Varsol. Brake or contac cleaner will be fine.
You are always going to get some fretting but if these holders have not been used very much and it is really noticeable it could mean your drawbar tension is too low. The belleville spring washers that retract the drawbar sometimes break and then the tension is lost. You should see if you can get someone to measure the tension. For Cat40 I think it should be around 1500lbs but I am not positivre about that.
An open mind is a virtue...so long as all the common sense has not leaked out.