When the .trash folder contains read-only directories or files, it cannot be emptied with the "Emtpy Recycle Bin" button of "File Manager". Instead it throws errors that Linux "rm" cannot access the files or directories for removal.

As these files and directories are in the trash folder, I propose to delete such files anyway as otherwise a user without console access or limited knowledge (such as using FTP to change file permissions, if that is possible at all for the FTP user account) can't ever remove such files.