woopsie-upload-all process consumes cpu 100%

You probably have some processes creating crash-reports with large files. Look in /var/crash/ if there are some big crash-reports. When those are being uploaded to canonical it can produce a high system load.

On my system I had a 361MB file:

_usr_bin_baloo_file.1000.crash

So baloo, the kde search-assistant created a problem.

I don't need baloo on my Ubuntu system (it was installed as a dependency packet when I installed KDE dolphin) so I disabled it with

balooctl disable                  # stops the service
rm -rf .local/share/baloo/        # removes the index files; they can be several GB

and delete the crash reports with

sudo rm /var/crash/*baloo*

Uninstall the whoopsie and apport services. These are crash reporting services which can face issues.

sudo systemctl stop apport
sudo systemctl stop whoopsie 
sudo systemctl disable apport
sudo systemctl disable whoopsie
sudo apt-get remove apport whoopsie