Is it a flash VM? Power down the system and pull the board!
Seriously though, with early systems, it will cycle 4 times and then xfer to the attendant. Is this what it is doing? Is it forwarding to x100 & then no answer returning again to the main greeting?
On later systems, it follows the Time Out setting that the programmer set up.
Also, depending on how it was set up, you might just put the system attendant through the Day/Night/Special modes. Depending on how it was set up, the programmer may have missed one of those settings and the factory default may offer some relief.
We may be able to offer more help if you tell us what greetings/announcements are being heard. Custom ones? Factory ones?

- Dave S. -

You can never appease your ideologue opponents.