downloading file encounters error occasionally

I use ftpserverlib as the ftp server. I got an strategy error onccasionally. For example: I download the file `/ab/abcdef/abcd-ef/9900/01-01/001_033/20250702_100514/AbcdAbcdAbcd/HUGE2.bin`, and go the error
```
err: short response: 50702_01/001_033/20250702_100514/ACINB4.bin: file exists
```

Thanks in advance for any advice!