The issue is resolved.
The fact is that it may be recommended to stop the services (mainly distribution and qlikview server) before undergoing any deletion of files.
So we could follow the steps:
- stop and delete any unwanted task
- stop the 2 services
- backup and delete the related source/user documents
- restart the 2 services
Also it may be better to backup the qvpr folder (just in case).
If anyone has also any suggestion or tip, it's surely welcome.