Odd one - extension cannot connect

FreePBX 15/ Asterisk 16.13.0

I have a set of custom extensions with FMFM enabled going out to cell phones. One extension that had been previously working all of the sudden stopped. When I called the number I would just get a fast busy reject. I ended up adding an inbound route (previously had no inbound routes for any of the extensions) for this one extension and the calls hit the extension properly. I delete the inbound route, it goes back to the fast busy. The extension looks perfect, and works perfect with an inbound route, but I don’t want to have to add inbound routes needlessly. All other extensions built the exact same way all work without the inbound route.

One thing I noticed about the failed calls is when I watch the log, they don’t even get far enough to record in the CDR. When I observe the log for a failed call, there is no errors, but it seems to stop abruptly at

freepbx AGI Script agi://127.0.0.1/dialparties.agi completed, returning 4

Anyone have any ideas of what might be going on?

The extension has been locally set to otherwise reject connections?

Not that I can tell. There is no endpoint, it just goes to a cellphone. I looked though the extension options and compared to a known working one and everything looked identical. I also compared using asterisk -rx "database show" | grep EXTENSION
And that looked good too. The inbound route makes it ring without changing anything on the extension, so I was skeptical I would see the issue there.

Does it happen when you dial the extension directly as well?