Resolved in: WPML Multilingual CMS 3.9.4
If your web server is running on a Windows based machine, there is a limitation related to the maximum path length of 255 characters.
This is a known limitation of Windows that is related to the file systems (both Fat32 and NTFS are affected).
However, this limitation is reached in some cases because of some WordPress functions in our plugins for updating WPML from the back-end automatically.
You can read more and follow the issue at the WordPress trac https://core.trac.wordpress.org/ticket/34938.
As a workaround, it is advised that you update the WPML plugins manually by FTP.
Otherwise, you can deactivate and delete the WPML plugins, then upload their up-to-date versions in Plugins->Add New.