Extensions randomly not going to VM

Freepbx distro
PBX Firmware: 6.12.65-29
PBX Service Pack:

Random extensions with voicemail enabled suddenly rings and rings and rings and rings… but not going to VM. I’ve had to change the extensions at the bottom if unavailable to go to VoiceMail: ext# unavail, ext# busy and ext# unavailable (ext # equals the same extension that I’m setting it in manually). In other words, the extension’s VM is enabled and the default Optional Destinations settings “Unavail voicemail if Enabled” ETC, aren’t working.

Has anyone else run into this? This server is driving me insane.