我终于找到了问题！

事实证明，我们使用Unicode编码，而不是ASCII或UTF-8编写文件。更改FileStream上的编码似乎解决了问题。

It turns out that we were writing the file using Unicode encoding, rather than ASCII or UTF-8. Changing the encoding on the FileStream seems to solve the problem.

感谢大家的所有建议！