K, then open one at Issues · platformio/platformio-core · GitHub
Yes it is, you can always manually activate the penv that PlatformIO is installed in and do a pip-uninstall of the old PlatformIO core and a pip-install of a fixed version of the core.
Assuming Linux paths:
# for linux
cd ~/.platformio
source ./bin/activate
pip uninstall platformio
pip install "platformio==5.1.1"
see platformio · PyPI.
Of course you should disable auto-update in the PlatformIO VSCode extension settings then too.
Also see Lib not found with last versión Core change? Home change? Framework? - #2 by maxgerhardt.