I have the same issue with a LaCie Rugged 5TB USB-C HDD, and a Mac mini M1 running macOS Sonoma 14.3. I've done a very long investigation with the Apple Support team and Genius Bar, and with Seagate support chat. My findings so far for my issue, in case it's helpful:
- Easy way to reproduce: put the computer to sleep and wait 3 minutes. There should be a popup.
- As someone mentioned, after some days, it may start failing even when working with it. I get a popup every 2 minutes, constant rate. Restarting the Mac fixes this issue (restart in safe mode to restart the NVRAM just in case), and it's back to just failing on sleep.
- It happens with other Macs, on macOS Sonoma. We tried other Macs in the Genius Bar.
- It DOES NOT happen when using a USB-C to USB-A cable.
- It DOES NOT happen when using a 240W thunderbolt charge cable (the £29 cable).
- It does happen when using the expensive (£75) Thunderbolt 4 data cable (100W according to the specs).
I called Apple support again. The engineer explained that when you connect the drive to the computer, there’s a handshake that determines whether to use Thunderbolt, or regular USB-C. Even if the port looks the same, Thunderbolt and USB-C are actually different connections. The Mac must think it’s thunderbolt even if I use a regular USB-C cable. And then it’s when it becomes unstable. When it goes to sleep, it tries to keep a register of the connection so it doesn’t have to do another handshake, or spark a new connection again. Then, when it wakes up it sends data as it was Thunderbolt, when it’s not.
That’s the explanation I got and I was suggested to keep using the 240W thunderbolt charge cable. That doesn’t seem to explain why it didn’t work with the Thunderbolt 4 cable, though.
However, Seagate asked me to do some speed tests with the different cables. If you are doing this, I recommend using a big file to get consistent results. I zipped my local Movies folder, and that gave me a 1GB ZIP file. To test the copying speed from the Mac mini SSD drive to the external drive, I used rsync. You can use it like this (“LaCie 5TB” is the name of my HDD):
rsync -ah --progress ~/Movies.zip /Volumes/LaCie\ 5TB
I tried with the Apple cable I got in the Apple store, and with the original LaCie cable:
- With 240W thunderbolt charge cable: 36.87 Mbytes/sec
- With USB-C to USB-A adapter cable (for reference): 38.21 Mbytes/sec
- With USB-C cable from LaCie: 123.62 Mbytes/sec
So it’s much slower with the charge cable, as slow as using USB-A 😢 But I can’t reliably use the LaCie cable. Or the £75 Thunderbolt 4 data transfer cable. Seagate says the drive is compatible with both Thunderbolt 4 and USB-C. The Mac Mini M1 port is Thunderbolt 3.
Seagate escalated this issue and they told me to wait 24 hours. I will also try to contact Apple again, because I'd really like to use the faster speeds.