All of my backups are failing verification now. What logs do I need to get to you @uroni so that you can help me out with this?
The errors I am seeing in the logs are:
Creating hardlink from "D:\Client Backups..." failed. Loading file...
and
Hashes for "D:\Client Backups..." differ (client side hash). Verification failed.
Ellipsis added for the purpose of anonymization. I can get you further logs if you need, just let me know.
Did this error start to occur after the client updated to 1.4.6 ?
You can send the logs to martin@urbackup.org . More extensivie logging is probably needed to identifiy the error.
If the error occured with the 1.4.6 update a full backup may fix it.
I think it started with the server update to 1.4.6, but the rest of them started it after clients updated to 1.4.6. If I trigger a full file backup, will it still pay attention to the hashes and not download everything all over again? 4TB of data over a 15Mb/s pipe will take a little while…
Yes, it will use the client-side hashes.
One more question while I have you, why does it take so long to stop a file backup through the web interface?
It only checks at certain points in the backup process. It could be checking more often, but that would be some implementation effort, which may not be justifiable.
Fair enough. When it is sitting there choking on a backup that is failing, there is no way to kill it to fix it. You can apparently only wait for it to fail.
I understand though. No worries and keep up the good work. 
I still have backups failing on doing a full-file backup. Client-side hash failure. What logs would you like in order to help me with it?
Send a few to martin@urbackup.org please. As much as you are confortable with.
Hi was the problem solved ? I have a Debian server and a Windows 7 server remotely connected on Internet and no backup has succeeded. Here is an extract of the log I receive in the middle of the night (14025 errors on 14025 files):
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2412002.FXD” differ. Verification failed.
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2412003.FXD” differ. Verification failed.
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2412004.FXD” differ. Verification failed.
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2434001.FXD” differ. Verification failed.
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2439001.FXD” differ. Verification failed.
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2439002.FXD” differ. Verification failed.
Erreurs
24.01.16 00:02
Hashes for “/opt/backup/urbackup/Papa-PC/160123-0922/Documents/Fax Delrina/2466001.FXD” differ. Verification failed.
This is a complete backup. I set the Verify file backups using client side hashes, Periodically readd file entries of internet clients to database, Calculate file-hashes on the client, End-to-end verification of all file backups.
Thank you for your help