External HD Drives Improperly Eject with High Sierra

Why are HDs using a Thunderbolt 3 to 2 adapter or bridge improperly disconnecting randomly and more frequently?

Here's my journal of experiences. Perhaps, Apple can use this to identify the issue. Because $50 is a lot to pay for an adapter that does not work anymore.

» With a 2013 iMac running El Capitan my two Seagate external HDs were using thunderbolt connections and were solid.

» I upgraded to the 2017 iMac running High Sierra out of the box (10.13.1). The two Seagate drives were daisy-chained using the Thunderbolt 3 to 2 adapter. The hard drives were working perfectly.

» It was after I updated to a 10.13.2 supplement that the problem started to occur randomly. When the drives were not being accessed for a bit usually. The drives would drop out and the Improper Ejection Error would appear. I was concerned about the hard drives failing (but BOTH at the same time?). They passed every examination test as being in top working order. So, I replaced the cables — another wad out of my pocket to Apple. To no avail.

» 10.13.3 came out. Perhaps this will take care of the matter. Just the opposite. It has become worse. It is more regularly disconnecting the drive and giving the Eject error.

» 10.13.3 supplement update came out and I installed it on February 21 2018. Its now even worse! In some instances – once the external Seagate drive appears on the desktop and within less than 2 minutes, the drive is gone and the Unexpected ejection error appears on the screen.

In every case, I have to disconnect the drives. Power them down. Then plug them in and power up for them to return. I can immediately unmount them and check them in DiskUtility. They are fine. Remount. And down they go.

» One commonality I see in all complaints.

Everyone seems to be connecting to the Thunderbolt 3 port with adapters — such as the Apple Thunderbolt 3 to 2&1 adapter. And all are having the same issue.

» The Seagates are the Flexdrive units with multiple base connectors. I switched the drives to the standard USB 2.0/3.0 base connector. Neither drive failed for the entire day and never ejected. I took another drive I was using via USB 3.0 and connected it to the Tbolt adapter. It dropped out just the same.

Perhaps the issue could be found somewhere just after the 10.13.2 supplement updates?

Perhaps I can downgrade to 10.13.1 or 10.13.2?