Problem with external drives safe to remove not working.

My brother has a problem when ejecting external drives that he does not get the notification to safe remove the drive.
When he then ejects the drive and starts the pc, he gets BSOD DRIVER POWER STATE FAILURE.
We have tried the external drives on another pc and they are working normally.
When he restarts the pc with the external drive connected all is working normally but when he clicks to eject the drive the drive disappears from the hidden icons without the notification to safe to remove and does not get removed from the Devices and Printers on the control panel.
When he tries to connect the drive to the pc again he gets a yellow exclamation for the drive in Device Manager.

The issue only happens after he ejects the drive.
Any ideas why this is happening?

Answers to @dalchina

Hi, to clarify, do you mean that the PC only boots with this drive in place?

No, the pc boots normally, when an external drive is disconnected and he tries to shut down the pc Windows will not shut down, it will display the BSOD and will take a long time to restart the pc, but the external drive will show with a yellow exclamation mark when connected again.

What happens if you use a different (blank) drive?

The same thing happens as it is a Windows issue not a drive issue.

What happened that led to this? (History is so often unstated by posters, although I appreciate here this isn't your PC).

He uninstalled SyncToy

If this started recently, has he tried using a System Restore point?

He has but it did not work.
Drives are monitored in real-time by HD Sentinel drives are working normally. Sentinel does not flag any issues with the drives.

Answer to @zebal
The option to safe remove is enabled.

Things have gone from bad to worse.
My brother, bless him he is eighty seven years old but still gets to use his pc but not the very technicalities. I help him via remote with TeamViewer whenever I can so please have some patience!
After the System Restore the pc now goes into a loop with the BSOD DRIVER POWER STATE FAILURE, and auto repair but does not repair anything and we cannot get into Windows.
I can only envisage having to clean install Windows install Macrium Reflect and create a Macrium Rescue Media and then restore an image backup from before the issue started.

Or if someone has a better idea I would be most grateful.

dalchina said:

If you have a disk image (of all Windows' partitions - typically 4 for a UEFI installation) then...
- you (or anyone) can create a bootable Macrium R disk
- and then restore the image that was created.

No need to clean install Windows if you can create one using another PC.

Yes I agree the best option is to use MR Rescue Media and restore the latest backup which is two weeks old.