Poor network visibility. How to optimize?

Question

Active Directory

Good afternoon good people. I faced such problem. There is an office. They have a bunch of computers connected to the same network. There is a shared access between users to each other to virtual disks connected from Synology. Each account for each user is connected from Active Directory. The point is. When one user accesses another user's iSCSI disk, for some reason it starts to require the password of the Active Directory "Administrator" account from time to time. And even later, for some reason, it started to log in for a very long time, and does not go to disks for general access at all. But the most interesting thing is that the user's IP enters PERFECTLY. With what it can be connected?
PS I explain very badly, I apologize for that