This is actually a feature. Evertime someone tries to write to the database it restarts the backup to allow the write. I can see how this can cause more problems then simply disallowing writes for a time and will change it to that…
If you can, backup the UrBackup databases by some other method e.g. by using the UrBackup client combined with a snapshot method e.g. LVM.
Btw. this is now a release. This means bug fixes will take longer if they are not critical such as this one.