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“Disk Not Ejected Properly” – USB3 – iMac Pro – Sleep/Wake

There are hundreds of discussions about a “Disk Not Ejected Properly” Alert. And there are lots of suggestions of how to fix from changing Energy Saver settings to firmware updates on external disks.
None of the existing solutions worked for me with a 2017 iMac Pro and a Seagate Backup+ Hub 6TB disk. Every time the computer goes to sleep the error would occur when the iMac was woken up. After the error the disk volumes can’t be remounted until the iMac was restarted. Clearly not a good situation.
Since this was a new iMac, there was only a few apps installed. Testing confirmed that with a clean MacOS 10.13.5 installation the external disk sleeps and wakes OK, without error. So it was one of a dozen apps that was installed that causes the problem.
For me, the problem was caused by the installation of Epson Printer Software Update 3.3. This package installs something called “/Library/Extensions/EPSONUSBPrintClass.kext” which loads “/Library/Printers/EPSON/CIOSupport/EPSONUSBPrintClass.plugin”. Something in this package is doing something bad to the USB interface on the iMac Pro. Removing the kernel extension EPSONUSBPrintClass.kext solves my problem.
Since I use wifi to connect to the printer, I’ve not seen any adverse effects from removing this kext. But if you use USB, I’m not sure what functionality you’ll lose.
Update (23 June 2018): Removing the kext didn’t completely fix the problem. I have set my Apple Watch to unlock the Mac and this, in combination with a Bluetooth keyboard and mouse/trackpad is compounding the complexity. So this is what I’ve done to problem solve the error: