Mac mini M4 as NAS – many Finder / SMB bugs between Macs, any solutions?

I recently bought a Mac mini M4 (base model) and planned to use it as a small home NAS with several external HDDs attached.However I’ve been running into many Finder / SMB issues when connecting from another Mac. Ironically, a Windows client works perfectly while the Mac-to-Mac connection is very unstable.

Important note:

All of the issues described below occur frequently but not 100% of the time. Sometimes everything works normally, but the problems come back randomly after reconnecting, rebooting, or after the drives have been idle.

Setup

Server:

Mac mini M4 (base model)

External HDD attached and shared via File Sharing

Clients:

MacBook Air M3 (24GB)

Windows 11 laptop

All devices are running the latest OS versions.

Network:

Wi-Fi (~800 Mbps)

1 Gbps Ethernet

40 Gbps Thunderbolt Bridge (manual IP)

So network bandwidth is definitely not the issue.

All share permissions, users and File Sharing settings are correctly configured.

Issue 1 – Thunderbolt Bridge reconnect bug

I created a Thunderbolt bridge between the MacBook Air and the Mac mini and assigned manual IP addresses.

On the MacBook Air I used Connect to Server with the Thunderbolt IP of the mini.

Everything worked perfectly at first.

But after unplugging and reconnecting the Thunderbolt cable:

• both machines can still ping each other
• Finder shows connection failed

If I manually reconnect:

• the share appears to mount
• clicking into it loads nothing
• Finder shows a “Connect As…” button
• clicking it immediately unmounts the share

Issue 2 – external drive share disappears after Mac mini reboot

When connecting through Wi-Fi or LAN IP:

• the share works normally

However after rebooting the Mac mini:

• the external drive is mounted and accessible locally on the mini
• but from the MacBook Air the share disappears or cannot be opened

Issue 3 – Finder network discovery broken

Normally the Mac mini should appear automatically in Finder under Network.

It does appear, but when I click it:

• the window is empty
• there is a “Connect As…” button
• clicking it does nothing

Issue 4 – external HDD sleep problem

The Mac mini has an external mechanical HDD attached, and “Put hard disks to sleep when possible” is enabled.

After the drive sleeps:

• when accessing it from the client, the disk does not wake up
• the folder simply never loads

Only when I open the disk locally on the Mac mini Finder does the drive spin up.

Even after the disk is awake:

• the client still cannot open the folder

Strangely:

• connecting via Thunderbolt bridge IP works
• connecting via LAN IP fails

Other issues

There are also many smaller Finder issues:

• opening a video file over the network sometimes takes over a minute
• Finder and QuickTime frequently show the spinning beachball
• sometimes shares randomly disappear

The strange part is that a Windows 11 laptop connects to the Mac mini perfectly:

• shares are discovered immediately
• external drives appear correctly
• reconnecting after reboot works
• everything stays stable

So ironically the connection between Windows and Mac is better than Mac and Mac.

Has anyone successfully used a Mac mini as a NAS without running into these Finder / SMB problems?

Are there any known fixes or workarounds?

At this point I’m considering returning the mini, since using it as a NAS was one of the main reasons I bought it.

Any suggestions would be appreciated.