I have narrowed it down to one line of code:
ctypes.create_string_buffer(16)

That is enough to create 7 objects that have reference cycles.

[<class 'ctypes.c_char_Array_16'>, {'__module__': 'ctypes', '__doc__': None, '__weakref__': <attribute '__weakref__' of 'c_char_Array_16' objects>, 'raw': <attribute 'raw' of 'c_char_Array_16' objects>, '_length_': 16, '_type_': <class 'ctypes.c_char'>, 'value': <attribute 'value' of 'c_char_Array_16' objects>, '__dict__': <attribute '__dict__' of 'c_char_Array_16' objects>}, (<class 'ctypes.c_char_Array_16'>, <class '_ctypes.Array'>, <class '_ctypes._CData'>, <class 'object'>), <attribute '__weakref__' of 'c_char_Array_16' objects>, <attribute 'raw' of 'c_char_Array_16' objects>, <attribute 'value' of 'c_char_Array_16' objects>, <attribute '__dict__' of 'c_char_Array_16' objects>]

So maybe the bug is in ctypes itself, not the uuid module.