I need some help with my thinking regarding an employee.  I believe we have two issues with him, one won't do and potentially one can't do.

The won't do are several incidents where he has been told by his manager not to do something and he has done it again!  His manager has spoken to him and made it clear that if it happens again we may instigate a formal procedure.

At the same time when his manager spoke to him about the won't do incidents, the employee also informed her that he was unable to take on any more knowledge and if he was trained on a new subject something else would drop out of his brain (I kid you not, this is what he said).

I advised the manager to speak to him to try and understand what his issue was and what we can do to help, ie did he need more training, a different way of being trained, etc.

The employee just re-iterated the issue that he can't take any more knowledge in and related it to a car fuel tank and he's nearly full and he can't take any more in.

We provide ERP software to small/medium size businesses and the employee's role is consultancy so he is liaising with new/existing customers to understand their processes and advise them on the appropriate solutions.  The role requires a wealth of knowledge and experience which is built up from previous experience and training etc provided by us.

I'm really not sure what to do here, my instinct is to put him onto a PIP or should I consider something else?  Is this a won't do as well, ie he is not prepared to learn anything else?

Regards
Rachel