This is a workaround, for  in the cases the upgrade of the software is failing.

The attached files include the TFTP client with the version 480 branch 2 file.

Unzip the folder to c:.

Start the application from the C:\tftpd32_480_b2 folder. Open the file tftpd32.exe.

Now the FTP application starts. 

Current directory should be: C:\tftpd32_480_b2.

Server interfaces show which IP your network cards have.

Open up the web interface to access the IP DECT 10. Login using Admin as user and password.

Under firmware update, you enter the information like the below picture. 
For me my local computer IP is, you will enter yours where you have your FTP. 
Keep in mind that the IP DECT 10 must be able to access the IP that you enter here. 
The firmware path is entered as Download, and then the version and branch.

Press Save/Start Update and wait for the led on the IP DECT 10 to flash (after approx. 1 minute). 

Give it a couple of minutes to finish. It should go back to steady green when it is finished.

Go to Home/Status to confirm that you now have Version 4.80 Branch 2.