Share your experience!
Now I just tried to do a manual backup to my SD card and to my mail, but it just stops at 50% like before.
That's very annoying!
use XPERIA COMPANION
http://support.sonymobile.com/global-en/tools/xperia-companion/
do not worry too much.
copy your data files manually; check that all the apps keep their settings in cloud.
That's my experience as well ... even with manual backup it gets stuck forever at 50%.
It will work though if you disable backing up of app settings.
I'm using MyPhoneExplorer for many years now to backup and/or synchronise my contacts, calendar entries, SMS, call history, ... even across different phones.
But I have found no way to save app settings this way. 
Works a treat for me, so far.
With photos on the cloud. Contacts on google account and apps from play should be quite safe.
Why the back-up app should take up so much space is odd.
And previous poster would seem to be correct. The storage count seems to get confused about apps on the SD card.
It looks like the problem with saving "Apps" is gone with version 23.5.A.1.291.
Now I can do a safety copy even with "Apps" enabled in the "save&restore" apps menu in a reasonable time. It doesn't get stuck any more at 50% and there is no excessive internal memory consumption any longer.
Thank Hardy,
You answer solved my problem too
Hi Dani_283,
if you're refering to the high memory consumption of the backup app the steps are the following:
Go to "Settings", select "Backup & restore", choose "Automatic Backup", scroll down and deselect "Applications".
Go back to "Settings" and select "Apps". Press the 3 dots in the upper right corner and select "Show system". Now scroll down until you find an app called "Backup & restore" and select it. It will probably report a huge amount of internal storage used. Press on "Storage" and then press the button "Clear Data".
Please not that with software version 23.5.A.1.291 deselecting "Applications" is no longer necessary.