When starting new position it is expected that there will be a learning curve.
But what happens after that period and the person fails to retain knowledge?
Personally I have witnessed this “Learning Tailspin” several times. Qualified indivduals who for rhyme or reason begin to fall into a learning tailspin.
This can happen at times to all people but how much time should be given to this person. As sometimes the only solution is to let the person sink to rock bottom.