How to resolve ValueError: The circuit contains non-deterministic observables

I constructed a part of the syndrome measurement circuit as follows using Stim. However, when I run dem = circuit.detector_error_model() and print(repr(dem)), I get the error message ValueError: The circuit contains non-deterministic observables. Why is that happening? What I want to achieve is that at the end of this circuit, if an odd number of qubits (0 to 16) have experienced Z errors, the logical observable flips, enabling the detection of Z errors.