No text output when exporting to PDF and when printing --- Toolbar icons disappearing

I create a new text document in Libreoffice with some text: ok;
Now: If i export it to pdf, the pdf file is full white, no text output, and same if i want to print it, i only got a white page. I tried to change the font and text color of the document without
sucess. (The printer works fine with other software just for info).

Also It must be a separate bug but i report it here anyway...The toolbars' icons occasionnaly completly disappear...

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: libreoffice (not installed)
ProcVersionSignature: Ubuntu 5.4.0-48.52-generic 5.4.60
Uname: Linux 5.4.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: LXQt
Date: Thu Oct 15 22:04:20 2020
InstallationDate: Installed on 2020-09-04 (41 days ago)
InstallationMedia: Lubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: libreoffice
UpgradeStatus: No upgrade log present (probably fresh install)