Problem with upgrading to latest version (0.62.1)

I’ve upgraded to the latest version of hassbian multiple times following the instructions on this page.

This time however, I get an error message when trying to run the pip3 install command. I cannot get pip3 to do anything after the source command has been run, but I can use it fine (e.g. install and uninstall packages) before the source command.
The error seems to be the same no matter which pip operation I try to execute.

UPDATE:
I did a pip3 uninstall homeassistant and reinstalled it manually.
Many of the dependencies had to be installed a new, for some reason.

Now I am down to this error when trying to start homeassistant (both as a service and via the hass command)

– Logs begin at Tue 2018-02-06 21:59:18 UTC, end at Tue 2018-02-06 22:03:05 UTC. –
Feb 06 21:59:33 hassbian systemd[1]: Started Home Assistant for homeassistant.
Feb 06 21:59:37 hassbian hass[516]: Traceback (most recent call last):
Feb 06 21:59:37 hassbian hass[516]: File “/srv/homeassistant/bin/hass”, line 11, in
Feb 06 21:59:37 hassbian hass[516]: sys.exit(main())
Feb 06 21:59:37 hassbian hass[516]: File “/srv/homeassistant/lib/python3.5/site-packages/homeassistant/main.py”, line 349, in main
Feb 06 21:59:37 hassbian hass[516]: args = get_arguments()
Feb 06 21:59:37 hassbian hass[516]: File “/srv/homeassistant/lib/python3.5/site-packages/homeassistant/main.py”, line 90, in get_arguments
Feb 06 21:59:37 hassbian hass[516]: import homeassistant.config as config_util
Feb 06 21:59:37 hassbian hass[516]: File “/srv/homeassistant/lib/python3.5/site-packages/homeassistant/config.py”, line 26, in
Feb 06 21:59:37 hassbian hass[516]: from homeassistant.util.yaml import load_yaml, SECRET_YAML
Feb 06 21:59:37 hassbian hass[516]: File “/srv/homeassistant/lib/python3.5/site-packages/homeassistant/util/yaml.py”, line 9, in
Feb 06 21:59:37 hassbian hass[516]: import yaml
Feb 06 21:59:37 hassbian hass[516]: File “/srv/homeassistant/lib/python3.5/site-packages/yaml/init.py”, line 2, in
Feb 06 21:59:37 hassbian hass[516]: from .error import *
Feb 06 21:59:37 hassbian hass[516]: File “”, line 969, in _find_and_load
Feb 06 21:59:37 hassbian hass[516]: File “”, line 958, in _find_and_load_unlocked
Feb 06 21:59:37 hassbian hass[516]: File “”, line 673, in _load_unlocked
Feb 06 21:59:37 hassbian hass[516]: File “”, line 669, in exec_module
Feb 06 21:59:37 hassbian hass[516]: File “”, line 773, in get_code
Feb 06 21:59:37 hassbian hass[516]: File “”, line 484, in _compile_bytecode
Feb 06 21:59:37 hassbian hass[516]: EOFError: marshal data too short
Feb 06 21:59:37 hassbian systemd[1]: [email protected]: Main process exited, code=exited, status=1/FAILURE
Feb 06 21:59:37 hassbian systemd[1]: [email protected]: Unit entered failed state.
Feb 06 21:59:37 hassbian systemd[1]: [email protected]: Failed with result ‘exit-code’.

Any help will be much appreciated!

TIA
KAL