Users not being automatically removed from the Newly Registered Users group under certain circumstances

For one of my forums, I've set up a system where newly registered users have to have their first post moderated. This has been achieved by setting forum permissions on the Newly Registered Users usergroup to the "Newly registered User" built-in role, and setting the "New member post limit" in User Registration Settings to 1.

Mostly, this works. However, there are a few occasions when the user is not removed from the Newly Registered Users group when said user's post is approved by a moderator, and a forum administrator then has to remove that user from the group manually.

Having observed this issue for a while (since the phpBB version where the Newly Registered User feature was added), I believe that I've picked up a pattern which may enable this issue to be reproduced:

• Each post in the moderation queue is approved singly.
• At the time of the user attaining the new member post limit, the user still has posts sitting in the moderation queue. If the user has no posts remaining in the moderation queue when the new member post limit is hit (and in our situation, this would mean that the user only ever has one post in the moderation queue to begin with), the user seems to be removed from the Newly Registered Users group correctly.

Please let me know if I need to provide further information. I am prepared to help test fixes if necessary.