This problem occurs when `copy.deepcopy(score)` is called. The issue results in a system error: ```shell SystemError: <built-in method __deepcopy__ of numpy.ndarray object at 0x7f23580174b0> returned a result with an error set ``` To reproduce: use this score : [here](https://github.com/musedata/humdrum-mozart-quartets/blob/master/kern/k080-01.krn) and call `copy.deepcopy(score)`.