Libssh SFTP download inside a thread crashes on sftp_read - c++

Question

I'm using the libssh library in MFC C++, specifically the SFTP wrapper. I have code working when not using threading, but I want to use AfxBeginThread to allow user action to continue.
I have confirmed I'm passing the exact same filenames and target save paths using the thread or not - I've tested this by hardcoding the file to save and the destination to save directly in BeginDownload().
Is there a specific way the SFTP wrapper for the libssh must be used to let the download perform within a thread? I would like to allow users to download multiple files at the same time from the same instance of the ssh objects, and just launch a new thread each time a file needs to be downloaded.
Here is what I'm using for the actual downloading. m_sftp_sesssion is my sftp_session object created upon logging in.
bool CSFtpManager::BeginDownload(CString filename, CString savefilename)
{
sftp_dir dir = sftp_opendir(m_sftp_session, "../../../directory");
sftp_attributes attrs = sftp_readdir(m_sftp_session, dir);
int access_type = O_RDONLY;
sftp_file file;
file = sftp_open(m_sftp_session, "../../../directory/myfile.zip", access_type, 0);
const char* x2 = ssh_get_error(m_ssh_session);
if(file == NULL)
{
int a;
}
int nbytes;
char buffer[1024];
FILE * pFile;
pFile = fopen(CStringA(savefilename), "wb");
nbytes = sftp_read(file, buffer, sizeof(buffer)); //this is crashing inside a thread
while(nbytes > 0)
{
fwrite(buffer, sizeof(char), sizeof(buffer), pFile);
nbytes = sftp_read(file, buffer, sizeof(buffer));
}
fclose(pFile);
sftp_close(file);
return true;
}
Here is my login method where my libssh objects are being set in member variables for later use. Included is a commented line calling my BeginDownload. Calling it outside a thread (i.e. clicking a login button) does work.
bool CSFtpManager::login()
{
int verbosity = SSH_LOG_PROTOCOL;
m_ssh_session = ssh_new();
ssh_options_set(m_ssh_session, SSH_OPTIONS_HOST, "ftp3 host..");
//setting username and password...
ssh_options_set(m_ssh_session, SSH_OPTIONS_LOG_VERBOSITY, &verbosity);
ssh_options_set(m_ssh_session, SSH_OPTIONS_PORT, &m_iPort);
int x = ssh_connect(m_ssh_session);
const char* x2 = ssh_get_error(m_ssh_session);
if(rc != SSH_AUTH_SUCCESS)
{
return false;
}
m_sftp_session;
m_sftp_session = sftp_new(m_ssh_session);
//Calling BeginDownload here does work
//BeginDownload(L"file.txt", L"T:\\file.txt");
... }
Here is what I'm using to call the exact same function via a thread
CWinThread* pThread2 = AfxBeginThread(BeginSFTPDownload, bundle);
And the method being ran via the above:
UINT CMainFrame::BeginSFTPDownload( LPVOID pParam)
{
pSft->BeginDownload(L"test.txt", L"T:\\test.txt");
return 0;
}