Quicklook not letting external hard drive eject

Hi community members

I've had a bug bothering me for a while. My external hard drives won't eject safely. They have to be Force Ejected

(Screenshot of the error message. Norwegian System Language)

I've tried some different solutions.

What's Keeping Me, an app telling you what files are open on a folder og volume shows that either Spotlight or QuicklookUI that's using the external volume. Quicklook and Spotlight preferences has been deleted and reset.

Excluding the volumes from Spotlight fixes the Spotlight indexing keeping the disk unmountable, but the Quicklook problem persists if an file on the disk has been previewed by Quicklook. I've even reinstalled the macOS High Sierra 10.13.3 Combo update to flush out any broken files.

The external volumes behave in the same way with Disk Ownership on or off.

The disks is formatted in Macintosh HD (Journaled CASE-Sensetive) and ExFAT.

I've tried repairing the disk with Disk Utility First Aid. No Errors.

Anyone else that has a suggestion or solution to this bug? Experienced it yourself?

Best regards

Erling