Helping out nice but incompetent coworker

Some context, this coworker has been known to ask questions over and has been in the position for more than a year. Some other team members have complained to our manager that he keeps asking the same questions over and over. (this is hear say, as I can't confirm that a formal complaint was issued in writing)

To be fair to this one teammate, our training manuals and employee procedures aren't the clearest.

Now to the moral dilemma. This one team mate is nice, and I've tried to help them and help them help themselves several times, but for some reason it's not sticking. I tried giving them cheat sheets, challenged the knowledge shared with them to be sure it's sticking, but they still keep coming to me with questions.

I'm never one to turn down someone who needs help, and I have hard time saying no to people, but I'm wondering if I should bring this up with my manager during our next one on one. This teammate has also voiced to me in confidence that they didn't receive a good performance review, so I dont wanna be the last complaint that gets them fired...