It's almost certianly a "smart quote" character for an apostrophe, which on Mac is ASCII code 213 and on Windows 146.

You probably need some kind of regex-loop to fix four characters at least, single and double opening and closing quotes. If it's Mac for instance, then 210 and 211 should be replaced with " and 212 and 213 with ' -- but this is the quick fix, not the proper one.
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