The first occurrence is ok, but the second and third contain an 0x02 byte (when I save from this URL using Firefox and read the file as bytes using Python), as in my first post. validator.w3.org gave me enough context to locate the first 0x02 in the line.
U+002610 is just the box symbol that something is replacing it with (but not in the RSS).
I asked for the post to be repaired as I didn’t see me getting my subscription working without. I can send you my saved bytes if it would help.