Finder error -36 when copying from data Blu-ray to HD
So I came up with a sort-of answer here. In short, a full copy of the Blu-ray was possible using the ditto command line tool:

ditto [source path] [destination path]


During the operation ditto does show errors (in my case Unknown error: 10000), but it does continue with copying the remaining files.

More detail

In figuring this out I started by inspecting the Console for errors during a Finder drag and drop copy. Sure enough an error was logged:

30/10/2015 19:54:57.000 kernel[0]: udf error: errno_t UDFFileNode::ReadPathComponent(uint8_t *, off_t *, bool *): Incomplete path component


On searching for 'mac udf error readpathcomponent error' I found this post on Adobe's forum which pointed to symbolic links being the problem.

Two types of file causing me an error were iPhoto and Photos Library files, and sure enough, within their packages there are symbolic links to certain .db and .apdb files. It appears the Finder attempts to resolve those links when drag and drop copying, but when it can't find that data (which isn't on the Blu-ray) it stops the copy and throws a -36 error.

To confirm this I looked for another way to copy the files, finding the ditto tool. Supporting my theory, the errors ditto threw up during the copy all related to symbolic links. So this might be a Finder bug rather than a hardware problem.