seagate disk not ejected properly

Just want to assure you this isn't just Seagate drives. I have lost Time Machine backups repeatedly due to "disk not ejected properly errors" when using a shared disk on a different Mac to back up over WiFi. It happened with my earlier Intel MBP, and is now happening with my M1 MBP running first Ventura and now Sonoma. The backup drives I use have been WD, they are plugged into electricity, they are less than a year old. I've also tried using an SSD drive as backup--same thing. These discussion forums provide no assistance, unfortunately, because most suggestions are basic things I've tried, being a Mac user for 30+ years. I've tried Apple and Apple Stores and they have not had an answer. I can't tell if Apple even knows this is a major problem.

Anyway, you can find complaints about this all over and many of us feel you pain. Just not sure where Apple itself stands on it.

How old is the external drive? Is it powered by the Mac? If it is powered by the Mac, those unexpected ejections can be a symptom of an external drive mechanically wearing out. They require more and more current from the Mac as they get older and eventually the connection becomes marginal.

Try to see if you can change your settings to never allow external drives to sleep. This is in the Advanced settings under Battery in System Settings. Also set the laptop to not sleep, prevent automatic sleeping when display is off, in Advanced settings under Display System Settings. With all this sleep prevented, is the problem gone? If so, you can use it like this, or try turning them back on, one at a time, to see which caused it.

(If you are using an older system than Ventura, these options may be found in different System settings/preferences.)

If you are using Seagate drive management tools/software/firmware, that might also be the problem as it may interfere with the MacOS settings above, so uninstall the Seagate software if you are using it.

When you first Mount your external drive, MacOS copies the Directory into RAM memory and marks the copy of the directory remaining on the drive as "checked out" indicating it is no longer the latest version. Then MacOS can make rapid file transfers, without having to re-write the directory after each transfer. The copy in RAM becomes the accurate copy.

Ejecting or un-Mounting the drive correctly copies RAM memory Directory back to the drive and makes it 'checked back in'. If your computer crashes or you pull out the cable before the Directory from RAM memory is "checked back in" by copying to the drive, you will later get the message "drive not ejected properly."

Many older Bus-powered drives do not elegantly fall back to the modern standard of transitioning to USB standby power while the Mac sleeping. Because the drive is not transitioning properly, dropping its USB power means it disconnects, rather than Ejects.

When the drive reconnects, the Mac sees the drive as improperly disconnected, and the Directory on the drive is "Stale" This can generally be fixed with Disk Utility repair/first-aid.

The long term fix is to provide stable external power for a drive that can not transition elegantly through computer sleep, or be prepared for trouble if the drive is left connected when the computer sleeps. Or, modify computer sleep conditions (like never sleep).