Lightroom 6.14 can't import to Pictures folders

Hi - I'm running Adobe Lightroom 6.14 on Mac OS 10.13.5. Have recently encountered issues in importing pictures into Lightroom from both external card and even from another subfolder under Pictures. Lightroom does not import any images and reports "Could not copy a file to the destination folder because it is not writable."

I have confirmed that I have "read & write" authorization for Pictures and its subfolders, and I can manually copy a picture into the Pictures>2018 folder and I'm able to create a new subfolder for the relevant day. Permissions on the drive have been checked/repaired. Disk Utility First Aid didn't find any issues either.

Everything was working fine until about May 20 (date of last picture imports). Since then, no updates to Lightroom until the issue appeared. Only some Mac OS updates from the Mac App Store (Security Update?), but I don't see a connection.

Has anyone encountered the same issue?

Thanks,

Christian