I can't to describe how to reproduce the bug since it's highly CD-dependant. However, sometimes, cdir will print some random characters. I've merged the latest debian cdtool patches. The problem is fixed by these patches.
Created attachment 74414 [details, diff] Debian patch from cdtool_2.1.5-4.1.diff (sanitized for gentoo)
Created attachment 74415 [details] Updated ebuild.
Is this still necessary for cdtool-2.1.8? Test, and reopen if needed.