What to do about developers who don't following code standards consistently?

I have a junior developer on my team who is pretty inconsistent about adhering to our code standards for formatting. Unfortunately, we don't have a good linter or style formatter option (it's SQL and PL/SQL), so adhering to standards is a manual process. I will get code reviews with formatting that is wildly out of step with our standards.

When this happens, I have to go through and mark every case where he didn't follow the standard. Just marking one as an example and telling him to fix the others too isn't enough - he'll just fix one or two and miss all the other cases where he made the same mistake. I also frequently have to explain why his code doesn't meet the standard. He can't just read the standard and figure out why his code doesn't match it. It's pretty frustrating, and I feel that it's not a good use of my time.

I've spoken to my manager about this in the past, and her response is that my colleague will eventually do it the right way with enough feedback. But I don't think he actually will. In my experience, if I am really vigilant about pointing out every mistake, he will write better code... for a bit. But as soon as I start to relax, thinking the problem has been solved, he will revert to writing sloppy code again.

I feel like this is a management issue, but am I missing any other options for getting him to change his behavior?