Connection error on WP Engine

When uploading files to WP Engine, I receive this error:

`Error: Unable to exec`

This error has been [reported](https://github.com/yongkangchen/remote-sync/issues/137) before by WP Engine users, but I may know why it is happening. Can you let us know which ciphers the FTP process is using? WP Engine seems to only accept the following ciphers:

```
aes192-ctr
aes256-ctr
```