Reported by customer on issue 16663. A primary copy from LibreOffice results only in partial data when using vncconfig within a Xvnc session. Other programs works as expected so the problem probably relies in LibreOffice (timestamps or something like that). I verified that this also is an issue using Fedora 21 tigervnc packages so its not related to our build of Xorg version.
Retested and this still happens. Tested on RHEL 8 with LibreOffice 6.4.7.2 and ThinLinc 4.13.0.