Just adding a note for Bionic users, that the commit "cifs: Set CIFS_MOUNT_USE_PREFIX_PATH flag on setting cifs_sb->prepath." landed in 4.15.0-143-generic, causing the regression, and it has been reverted in 4.15.0-144-generic.
If you are experiencing any issues with 4.15.0-143-generic, please upgrade to the fixed 4.15.0-144-generic.
Just adding a note for Bionic users, that the commit "cifs: Set CIFS_MOUNT_ USE_PREFIX_ PATH flag on setting cifs_sb->prepath." landed in 4.15.0-143-generic, causing the regression, and it has been reverted in 4.15.0-144-generic.
If you are experiencing any issues with 4.15.0-143-generic, please upgrade to the fixed 4.15.0-144-generic.