There's missing detection for the python modules, marshal.loads and types.FunctionType and Fickling throws unhandled ValueErrors when the stack is deliberately exhausted.
An unsafe deserialization vulnerability in Fickling allows a crafted pickle file to bypass the "unused variable" heuristic, enabling arbitrary code execution. This bypass is achieved by adding a trivial operation to the pickle file that "uses" the otherwise unused variable left on the stack after a malicious operation, tricking the detection mechanism into classifying the file as safe.