GUI freeze & high CPU load

[Timmie]

On Linux Mint with version 0.68 I often get very high CPU load.

After the following actions, the GUI completely freezes:
* insert a new tag
* insert a URL

Similar happens with the portableapps version on Windows 10.

How can I help in debugging?

===

zim -D
INFO: This is zim 0.68
DEBUG: Python version is sys.version_info(major=2, minor=7, micro=12, releaselevel='final', serial=0)
DEBUG: Platform is posix
DEBUG: No bzr version-info found
DEBUG: Not running from a source dir
DEBUG: Set XDG_DATA_HOME to /home/HOME/.local/share
DEBUG: Set XDG_DATA_DIRS to [<Dir: /usr/share/cinnamon>, <Dir: /usr/share/gnome>, <Dir: /home/HOME/.local/share/flatpak/exports/share>, <Dir: /var/lib/flatpak/exports/share>, <Dir: /usr/local/share>, <Dir: /usr/share>, <Dir: /usr/share/mdm>]
DEBUG: Set XDG_CONFIG_HOME to /home/HOME/.config
DEBUG: Set XDG_CONFIG_DIRS to [<Dir: /etc/xdg/xdg-cinnamon>, <Dir: /etc/xdg>]
DEBUG: Set XDG_CACHE_HOME to /home/HOME/.cache
DEBUG: Connecting to /tmp/zim-HOME/primary-0.68-e63203e4
DEBUG: Dispatched command (u'-D',)