WordPress website backups using BackWPup plugin complete with the following warnings:
WARNING: File name "wp-content/pluglns/woocommerce/packages/woocommerce-blocks/build/very-very-long-file-name.js" is too long to be saved correctly In Tar archive!
As the message suggests, the issue is caused by file name length exceeding the Tar archive limit. The same limitation affects Tar GZip archive format. The workaround was to change Archive Format to Zip in BackWPup backup job settings. This may slow down backup jobs somewhat, but Zip format doesn't have the same file/path length limitations.