\x0d is the character \r which brings the cursor to the start of the line, then \x20 is a space, so it overwrites the a with a space. If you're on a unix-y system you may want to consider just removing \r from your output/file since it's not needed if it's for text output. The \n "implies" it for *nix, but not for Windows.
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Answer by Eric Renouf for bash - why does \x0d\x20 erase the line
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