Permalinks occasionally change to double post_id instead of postname/post_id

Running a blog with 6 users, all with same user access. Despite resetting permalinks, some users publish posts that will show a double “post ID” (domain.com/12345/12345) permalink rather than the specified postname/post_id format.

Some posts work fine (domain.com/a-post-title/12345) when published but others do the above with no issues shown when uploading content or actually publishing the post.

There’s no pattern with the occurrences either. Sometimes they work, sometimes they don’t and it will be at different times of the day.

Any help would be greatly appreciated.

Cheers