Regularly getting The lock file could not be created error

Suddenly getting Error message The lock file could not be created for exclusive access by LibreOffice, due to missing permission to create a lock file on that file location or lack of free disk space.

I am the only user on my PC, it has only recently started, there is more than 75% free disk space on the drive.
Other errors are it then will not save files either.

Other disk-intensive programmes work OK

Any ideas?

The message you quoteded seems to clearly tell that you (the user as which you are logged in to the systen) has not the right (as stored by the system) to create a file in the folder containing the file you tried to open. Did you look for the rights on that folder granted to you?

Workaround: LibreOffice error "...insufficient user rights" in windows 10 - #8 by eddy_lt