Techniques for mentoring slow learners

I am in a lead position as a software developer but am having a really hard time with some developers on the team.

No matter how many times I calmly/politely explain what I perceive to be very simple mistakes I see with these members of the team, they constantly repeat the same ones.

Here's an example that I am constantly facing. I have Jira tickets that are being picked up by the team, they have a design, and they have a very clear description, yet somehow when I receive a PR for it, they've decided to do something different from the design given to them, or gone about the solution completely differently to what the ticket is suggesting they do. The suggestion is often there because the ticket outlines which existing methods/classes the developer should use so as not to re-invent the wheel. Yet somehow, they re-invent the wheel anyway.

This problem even comes down to very simple things like "Please create a PR when you're finished", or "please make sure the ticket is re-assigned and moved in the kanban board". – Regularly.

The most irritating thing about this is that they are perfectly adept engineers.

What techniques do those of you in positions of leadership have for managing problems like this within the team? Its tempting to just lay down the gauntlet and dare them to do it again but we all know that's just not the right attitude here! 😂

Apologies if this skirts the line of on topic content for the subreddit.