I think I figured out what is causing the bug to incorrectly reformat certain links such that they are no longer a link and end with "/[url]" being visible.
URL-only links work just fine:
But, I just noticed that if I save a named link:
[url=some_URL]text instead of URL[/url]
it gets saved as (notice the extra "url " at the beginning of the opening tag):
[url url=some_URL]text instead of URL[/url]
which renders as:
text instead of URL[/url]
It seems that the "=" immediately after the initial "url" is the issue. I emphasized "immediately" because I found that if I put a space between the "url" and the "=", and enclose the URL in double-quotes, then it works:
[url ="some_URL"]text instead of URL[/url]
So, I think there is a bad regex expression (or similar pattern matching dealy) on a filter / transform that is called on incoming text.