dCore x86_64 release candidates have been updated with an update in base to squashfs-tools. Previously, SCEs created from an .lst list file that exceeded about 1GB in size were showing squashfs errors on mount. Reducing the size of the SCE by reducing the contents of the .lst list file solved the issue, as well as updating mksquashfs from squashfs-tools to version 4.3. So squashfs-tools has been updated.
http://tinycorelinux.net/dCore/x86_64/release_candidates/