Firmware upgrade fails on T21P E2

[p.pasquino@technology4you.it]

Hello,
I have a strange issue here.
The pbx updated automatically a lot of T21P E2 phones to the firmware version 52.84.0.140.
In the structure I still have a phone T21P E2 at version 52.83.0.55
If I update it manually providing this firmware: https://downloads.3cx.com/downloads/v180....0.140.rom the procedure fails and somehow the phone remain at version 52.83.0.55 .
Do you have an upgrade path or a specific procedure that you can suggest me to get it to version 51.84.0.140 ?
Kindest Regards