The Roc's feather tiles in the default classic set when first opening up ZQ seem to have been corrupted a bit; if you look at them in CSet 0, you can see a few light blue pixels on them that aren't supposed to be there.
...The dates and filenames on some of my project backups that I've just now found out have the corrupted feather tiles suggest that said feather corruption's been in ZQ since at least RC2.5, unnoticed until now. <_<'