Unmounting SMB Shares; Server Shows as Idle

This doesn't happen every time, but quite often; so much so I'm questioning whether I made a huge mistake going with Apple for my File Server.

Server 10.11.4

Client 10.10.5

I mount a SMB share from the server.

I disconnect the share.

The drive is dropped from client and Server vanishes from "Connected Servers" list in sidebar, as expected.

But the server app shows the client as "Idle" under "Connected Users"

If the client tries to log back in via cmd-K, s/he doesn't get prompted for credentials and is just presented with a list of shares.

This is a problem if we want to re-login as a different user.

Also a security concern.

Any ideas?

Thanks!

Jeff