Listen to your gut. Doing specific tasks can be taught, but the drive to do those tasks will never improve. I recently had a guy who I wanted to like. I gave him every opportunity, paid him well, talked to him more times than I should have. In the end even with years of experience he just didn't get it. He knew how, but didn't care to his heart was not in it. A real shame cause he'll wind up never improving in life if he can't find drive. Either way I tried and tried and then one day he showed up to say he was done and quit on the spot. Really F'd us cause that week we needed every hand we had. Upon thinking back at the situation I knew from the first day, but I did not follow my gut.
Then his replacement I decided to go a different route. I found a kid who wasn't interested in partying and staying up late, he just wanted to make money. He's as green as they come. So the first few hours I'm thinking what did I get myself into. By the end of the first day he figured it out and was working uninstructed. By the end of the first week he had surpassed the drive and skill level of the prior 10+ year experienced worker. He is currently on his way to having a permanent job with us if he wants it.
My point is you already know what to do, but realize that if you are seeing things that your customers are seeing these things also and it is a reflection on you.