Firmware upgrade problem on W52P base

[Jocelyn]

Hi all,
this is my first post on this forum. I searched on the forum but could not find an answer to the following problem:
we have a recent installation of XiVO (based on Asterisk) in our company in France. We noticed that calling with the W52P does not generate ring back tone.
I noticed that this problem was identified in the release notes (bug number 5 for version 25.30.0.20)
We checked our base's version: 25.30.0.50, anyway we tried to upgrade to latest version but failed.

We do connect to the base's web page, launch the upgrade process, the base restarts, the web page becomes unavailable, then the base and its administration page are back, but ... the firmware version number is still 25.30.0.50 and not 25.50.0.20 as it should be... and the ring back tone problem is still there.

Note that this problem is not present on calls with Aastra 6731i.

Note that our handset is in version 26.0.0.7 for hardware and 26.50.0.20 for firmware after a successfull upgrade.

Pieces of advice are warmly welcome!
Merci beaucoup !