[trogggy]

I also tried to update, but didn't have any issues on my system. Nevertheless I think it is a kodi thing and not a skin thing. Any log-files? 

I've had this update problem in windows for a while.  I tried to reproduce it on a fresh install.
I set up a new install - leia rc2 windows x64 portable on windows 7.
Installed confluence from repo, then installed xonfluence dependencies and xonfluence 4.0.2 (all from zips)
Installed Hellyrepo.
Tried to update to 4.0.5
4.0.5 is downloaded and unzipped into a folder in addons/temp/, but that's as far as it goes.  There's an 'installation failed' notification.
Log is here.
See around 10:31:03 for installation errors:

ERROR: XFILE::CFile::Rename - Error renaming file ...\addons\skin.xonfluence
ERROR: Failed to move old addon files from '...\addons\skin.xonfluence' to '...\addons\temp\583ab7e3-7f1e-4f85-9a26-65f26dffb393'

It's not a big deal for me (and I don't know if this is a general kodi issue), but I'm happy to test / debug further.