"Unrecognized escape sequence" error with FastZip.ExtractZip

I have a C# app that extracts a single file from a .zip archive. When the extraction code (see below) is run from a console application it works without issue. When I am downloading the file from an FTP site and extracting, I get the following error:

{"parsing \"C:\\Data\\AppData\\Internal\\DataFeedProcessor\\WorkingFolders\\Feeds\\8\\preprocessing_files\\3\\TEST_CI_XXXXXX_YYYYYY2x.txt\" - Unrecognized escape sequence \\I."}

This is the code that is executing:

var fz = new FastZip();

fz.ExtractZip(sourceFile, Path.GetDirectoryName(sourceFile), targetFile);

The sourceFile and targetFile parameters are passed in as fully-qualified paths.

Searching the web has not turned up anything about this error... any help would be greatly appreciated!