I was working helpdesk and was mentoring a new hire.
Meta-professionally it went wrong almost immediately. We were inbound yet phone notification sounds were on, chronically late, messy inbox, paperwork disaster. Technical-wise, said she understood yet once asked to take a case flunked it. Always had an excuse. In the end she was let go when someone else from the team had to mentor her and backed my statements to the manager. Apparently the mentee had been complaining that I was the reason for her lack of progress.
What this taught me more than anything is that occasional defensiveness happens to the best of us, but I'll give a wide berth to people who are defensive as a rule and don't seem to want to learn. Tech requires constant improvement and if you are unable or unwilling to be taught by others, it's a bad sign.
Sorry you had such an experience!
Indeed the worst part of mentoring is noticing the unwillingness to learn of the other person...
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