From https://github.com/python/cpython/blob/main/Python/marshal.c:

41 is:

#define TYPE_SMALL_TUPLE        ')'

The difference between 41 and 169 is 128:

#define FLAG_REF                '\x80' /* with a type, add obj to index */

So the difference is the FLAG_REF bit being set. I'm not sure if that helps you or not.

In any event, this doesn't look like a bug. You might want to ask on python-list or Stack Overflow for more help.