MNS/IP/Parallel - MXOne weird results

[Hainsworth]

Hi all,
We have an external DDI going to an analogue extension (557) which has no phone attached. This is then monitored via an MNS onto a button on a dozen users' 6731i using BLF on 557

When a call comes into 557 it rings all extensions with the button mapped as you'd expect, one person answers it and the others stop.
Any subsequent calls to that number during the day will ring on all extensions, one person answers - but then the other handsets continue to ring with a ghost call. The button stops flashing, the screen no longer shows who's calling, but the handset will continue to ring until it's picked-up and put down.
First call after a system reboot will work again, every subsequent call will leave a ghost call.

Latest versions of everything as this is a newly installed system that the installers are still trying to get the bugs out of - can anyone point me in the right direction?

Thanks

 

[Hainsworth]

*sigh*
In case anyone else has the same problem and ends up here - the problem is the phone firmware.
Turns out we weren't on the latest version. We were actually on 3.3.1.1051, and apparently between then & 3.3.1.2235 (the latest as of time of writing) it's been fixed.
Uploaded the firmware to the server, rebooted the phones, all handsets now ring when you'd expect and hang-up when you'd expect.
Hope that helps.