Continuing to Ring After Voicemail

I have an odd issue that’s been bugging me for quite some time. Until yesterday I thought it was just my softphone but a Cisco 79xx series did it so I’m thinking it’s in the FreePBX somewhere.

The issue is that sometimes (say 50% to 70% of the time) a call will come in and ring for a very long time, even though the caller already went to voicemail. On my Bria softphone it seems to happen more often - but I use Bria more than I use hard phones, but last night at 5:30 a call came in and it was still ringing on my Bria the next morning. Yesterday a call came into one of my Cisco 79xx phones and it rang for about 20 minutes before stopping - again the caller had long since been sent to voicemail.

It’s not at all unusual for me to find my phone ringing for hours after I left my desk.

I have two FreePBX systems, a home and an office - the office box is hosted and the home box is a computer in my house - and both systems do this.

I know that without posting a bunch of sample logs and such that you can’t tell me precisely what may be the cause but do you at least have an idea of where I can start?