Connection To One NAS Unit Keeps Dropping

I have two NAS units that I have connected to my broadband router, and have mapped drives to them in Windows Explorer. The two NAS units are as follows:

1. Asustor AS-604T
2. Synology DS420j

The Synology one is purely for data storage, but the Asustor holds all my photo and video files, and has Plex running on it. Ironically, it is the newer Synology unit that is causing the issue, as I can be accessing it and for some reason, Windows explorer just stops responding (or the NAS does), and I eventually get a message that the drive can't be accessed. I get around this by just closing and reopening Windows Explorer. The odd thing is that it can lose/drop this connection within seconds. This is an example of what can happen:

. Open Windows Explorer
. Click on the '>' to expand the mapped drive
. Click on the '>' to expand the top level folder
. Click on the '>' to expand the next level folder
. Click on the next level folder name to view the folder contents

It's at this point that it happens. The mouse still responds and you can click on other folders or other drives, but nothing will happen. After about 30 seconds, it will display a message saying that the drive can't be reached. I get around this by closing and reopening Windows Explorer. On other occasions, it will work fine, and it can happen with any folder on the drive. Both units are setup as RAID 5, and both mapped in the same way. There are no power saving options enabled. I have even tried replacing the patch leads, and also tried swapping to different ports on the router. I've even tried swapping the two ports around, with the Asustor NAS plugged into the port originally used by the Synology.

What could possibly be different in the Synology setup that would cause this to happen?

I did a quick query using CoPilot on my Win 11 machine--
It is a rather lengthy response, and you may have tried some of its suggestions but here goes:

--------------------------------------------------------------------------------------------------------
It sounds like you’re running into the same frustrating issue others have reported — the Synology DS420 intermittently drops its mapped drive connection in Windows 11, even though other NAS devices on the same network stay stable.
Here’s a structured approach to troubleshoot and (hopefully) fix it:

---

## 1. Rule Out Network & Hardware Basics
- **Cables & Ports** – You’ve already swapped patch leads and router ports, which is good. Keep the NAS on a **wired gigabit** connection if possible.
- **Switch/Router Settings** – Disable any “Green Ethernet” or “Energy Efficient Ethernet” features that can cause idle disconnects.
- **Static IP** – Assign the Synology a fixed IP in your router or in DSM to avoid DHCP lease renewals breaking the connection.

---

## 2. Windows 11 SMB & Explorer Tweaks
- **Force SMB Protocol** – In DSM, go to **Control Panel → File Services → SMB/AFP/NFS → Advanced Settings** and set **Minimum SMB to SMB2** and **Maximum SMB to SMB3**.
- **Disable Opportunistic Locking** – In DSM’s SMB advanced settings, turn off “Enable Opportunistic Locking” to reduce Explorer stalls.
- **Reconnect at Sign-in** – When mapping the drive, check **Reconnect at sign-in** and use the NAS’s IP address instead of its hostname (e.g., `\\192.168.1.50\sharename`).
- **Credential Manager** – Store NAS credentials in Windows Credential Manager to avoid re-authentication delays.

---

## 3. Power & Sleep Settings
- **NAS** – In DSM, disable HDD hibernation temporarily to see if it’s related.
- **PC** – In Windows, go to **Device Manager → Network Adapter → Properties → Power Management** and uncheck “Allow the computer to turn off this device to save power.”

---

## 🛠 4. Test for SMB Session Drops
- Open a Command Prompt and run:
```cmd
net use
```
before and after the disconnect to see if the session is being dropped.
- Try accessing the NAS via `\\IP\share` in Explorer’s address bar instead of the mapped drive to see if it’s a mapping issue or a deeper SMB problem.

---

## 5. Narrow Down the Cause
- **Other PCs** – Test the DS420 from another Windows 11 machine. If it stays connected there, the issue is likely PC-specific.
- **Event Viewer** – Check **Windows Logs → System** for `Event ID 30803` or `Event ID 30804` (SMB disconnects) around the time of the drop.
- **Firmware & Updates** – Make sure both DSM and Windows 11 are fully updated.

---

**Pro tip:** Some users have found that disabling “Windows Explorer Quick Access” and turning off “Automatically search for network folders and printers” in Folder Options reduces random hangs when browsing NAS shares.


HTH,
telepro21

Thanks for the prompt response and the detailed information. As for the results, here goes:

1. All done or already enabled
2. All done except “Enable Opportunistic Locking”, which I've now disabled
3. I use Wi-Fi about 99% of the time, but have disabled the option as suggested in the ethernet properties
4. Ironically, when I did this just now, having had the laptop powered off for about an hour, the Synology was shown as being OK and the Asustor as being Disconnected. As soon as I opened Windows Explorer, and ran the command again, both were showing as OK
5. The only other laptop I have is a Windows 7 one that I use for car diagnostics. Windows 11 updates run all the time and the DSM was updated yesterday. There are no 30803 or 30804 errors at all, with the log file going back to November 2024.

I can't find where the two 'pro tips' options are, or maybe I haven't looked hard enough. But then why would it only affect one NAS, and not the other?

I'll see if anything different happens with the changes made in 2 above.

Have you assigned them both static IP's?

I have a DS212J and a DS220+ the latter would be just a 2 bay version of yours.

Both are now reliably connected, there was a slight problem with the older 2012 one which I found was due to User setup which I had used for about 8 years. Making it the same as the DS220+ solved it, a minor issue.
If I remember correctly Guest Users had to be disabled and another setting which I have forgotten.
I strictly followed the Synology instructions on the newer DS220+

DHCP server is in the Router, I make absolutely sure it the only one in the system, it works great no fixed addresses.
Both NAS boxes are Ethernet connected to Router.
Opportunist locking is enabled.
Host names are used.
SMB2 to SMB3 range.
HDD advanced hibernation is enabled.
Wired and Wireless network cards, both Laptops W11 and W10 have power savings and green ethernet enabled.
**Amateur muddle thru tip:**
File Explorer Quick Access is used.
Can't find the other tip at all.

Rollback_Jockey said:

Have you assigned them both static IP's?

Click to expand...

Yes, as previously mentioned.

Helmut said:

I have a DS212J and a DS220+ the latter would be just a 2 bay version of yours.

Both are now reliably connected, there was a slight problem with the older 2012 one which I found was due to User setup which I had used for about 8 years. Making it the same as the DS220+ solved it, a minor issue.
If I remember correctly Guest Users had to be disabled and another setting which I have forgotten.
I strictly followed the Synology instructions on the newer DS220+

DHCP server is in the Router, I make absolutely sure it the only one in the system, it works great no fixed addresses.
Both NAS boxes are Ethernet connected to Router.
Opportunist locking is enabled.
Host names are used.
SMB2 to SMB3 range.
HDD advanced hibernation is enabled.
Wired and Wireless network cards, both Laptops W11 and W10 have power savings and green ethernet enabled.
**Amateur muddle thru tip:**
File Explorer Quick Access is used.
Can't find the other tip at all.

Click to expand...

I've pretty much left the settings alone when setting these units up, so default settings. I'll have to see if disabling Opportunistic Locking has any effect. The hibernation and power saving I disabled, if they hadn't already been.

If the Quick Access is where you pin a folder to the Quick Access menu, then I do have that enabled, as I find it useful, and I have shortcuts to folder on both NAS units.