Curious why you would want to remove the device to begin with?  I too have a Fireface 802 on Windows and when I am done with my session, things are left as is.  I find it unnecessary to remove the device?

The eject function is only intended for removable storage devices wzB USB sticks, so that data - which might still be in buffers in the main memory - can still be written completely to the stick before removing the stick, so that there are no incomplete / corrupted files on the stick.

This is recommended for storage devices for these reasons.

With a recording interface this is unnecessary and in my opinion it is more likely to lead to errors if you remove the audio interface while the operating system is running.

The fact that it worked in the past can be due to all sorts of things, maybe just minor differences in the sound setup of Windows. To find out afterwards would probably be a difficult task. Basically it doesn't really matter, because it's not necessary anyway.

Please just do the necessary things on your computer and everything will work much better than overperforming and doing things you better shouldn't do.

Take i.e. care of a working backup / restore, this is better invested time.

It should be possible and I do a power cycle of my UFX+ after a firmware update without any issue.
Of course you should not have any application running, which uses the recording device like DAW, Music Player, etc.

But why ?! Simply shut down the PC, by this everything gets a clean shutdown.
And if the PC is off, then power off everything related to it.

Device drivers are eventually in interaction with the hardware and driver do not like it if you steal them the device during operation ... Therefore the natural order of things is to perform a clean shutdown of Windows before removing hardware.

The only exception is the USB bus because it has been designed to make it possible to plug and unplug devices easily EDIT: but also here, not if the device is actually in use via ASIO driver.
But if this doesn't work with the main audio card in the PC .. simply don't do it or simply do not use the eject function.

On the other hand, as I said, power cycle of an USB interface should not be an issue.
But I am not sure whether eject function does something additional which is perhaps not good for an audio device.
If it doesn't work then power cycle the device after firmware updates as I do.

Otherwise follow my advice to shutdown windows and then power off any other hardware.

See my EDIT in post #6 to be extra clear on this.

... The only exception is the USB bus because it has been designed to make it possible to plug and unplug devices easily EDIT: but also here, not if the device is actually in use via ASIO driver ....