windows 10 virtualbox 6.1.2 wierd cant copy / move webm files

[clive darra]

windows 10 virtualbox 6.1.2 wierd cant copy / move webm files out of vbox subdir

windows 10 file manager just hangs !

is this a windows 10 bug or is virtualbox locking the files in some strange way ?

[ValdikSS]

I just finally figured out the issue that hit me for several months.

The symptoms:

• Explorer hangs upon clicking (highlighting) certain files, including (and especially) webm video files recorded by VirtualBox
• Sometimes explorer hangs upon right-clicking some files or when hovering over "open with" menu
• Dllhost.exe constantly consuming 7-9% of CPU

Turned out that dllhost process is started by "thumbnail cache class factory", and it fails to create thumbnail for webm video file captured by VirtualBox (other webms don't have this issue).

If you unsure which file causes this issue a and don't know what to delete, download Process Explorer, run it as administrator, find dllhost.exe which consumes CPU, press View - Lower Pane View - Handles, and you'll see which file causes the issue. Delete it (it Explorer hangs and you can't delete it, kill dllhost without killing explorer), and it would work fine afterwards.