Do you use Dropbox or Microsoft OneDrive for your knime-workflow.
You should make sure all three of your meta folders are accessible
- the folder where the KNIME program is (you can just create a new one with a fresh version)
- The knime-worspace folder where all your workflows are which is the most important one and should not be corrupted
- The folder where KNIME stores the temporary files
All three must be accessible there must be enough space and they must accept complex folder names with special characters.
A clean restart or new installation might be an idea along with making sure your SSD is structurally ok.