Willing to spend more time on this - but the variable names chosen blind me - looks like a circle.

And, thinking about the address in the core dump starting with 0xd (segment 13) - confuses me somewhat - as from memory - I thought the shared library code/data converged on segment 14 (ie, addresses would begin with 0xe).

So, perhaps it is the 0xd* address that is killing everything.

See: https://bugs.python.org/issue43665#msg389923 -- as I am also still confused re: this line - looks suspect: with all arguments at 0xdddddddd

PyVectorcall_Call(callable = 0xdddddddd, tuple = 0xdddddddd, kwargs = 

0xdddddddd), line 255 in "call.c"

And also this line, and lines like it - notice the value for what looks like a variable for argument_count:

_PyEval_Vector(tstate = 0x22023cf0, con = 0x2000120c, locals = 
0x22023960, args = 0x220239f0, argcount = 3508213100, kwnames = 
0x22023cf0), line 46 in "pycore_ceval.h"
_PyFunction_Vectorcall(func = 0x220239f0, stack = (nil), nargsf = 
570572016, kwnames = 0x220239f0), line 361 in "call.c"
method_vectorcall(method = 0x10103bdc, args = (nil), nargsf = 0, kwnames 
= 0x20045994), line 119 in "abstract.h"