Well, I opened a ticket with emetrotel and it looks like they fixed whatever was causing the issue. Here's their response if anyone comes across the same issue.
Today at 11:14:24, the fax service started reporting that it is unable to configure virtual modems. The service declared them as not recoverable, the modem was reinitialized and this was repeated over and over again. Between the time the modem was reinitialized and before it was declared not recoverable, the status was reported as running. After that, it was changed to not running. That's why we saw the changing status.
I restarted the fax related services one more time - and watched the initialization sequence of each modem - all of them came up without a problem. Since this last restart, all modems are up and running without an issue. One fax was received since that time, too. Something was interfering with the normal initialization / configuration of modems before. We'd need to investigate further to determine what happened. At this time, the system seems to be operating normally.