SSHException Channel was closed intermittent behavior

We are connecting to a client SFTP and prior to this week had nothing but successful transactions.
We are now experiencing intermittent exceptions. We are calling this functionality from an Azure function, and the files are streamed from Azure storage, but i don't believe that has any impact on the issue.
I have tried both synchronous and asynchronous methods and had success locally, and on majority of live test cases, but when it fails, I don't have an idea of what the problem may be. Any thoughts would be much appreciated.

My code is below:

sftpClient.Connect();
var uploadPath = $"{sftpFolder}/{fileName}";
sftpClient.UploadFile(stream, uploadPath);
sftpClient.Disconnect();

Alternatively, I tried instead:

sftpClient.Connect();
var uploadPath = $"{sftpFolder}/{fileName}";
var returnVal = sftpClient.BeginUploadFile(stream, uploadPath, new AsyncCallback(x => FileTransferred(x, log, fileName, uploadPath)));

从已报告的 Connect()、UploadFile() 和 BeginUploadFile() 调用开始，将 Azure Function 中的间歇性失败与本地运行成功的情况进行比较。记录 SSHException 的完整上下文以及连接或传输条件；完成标准是确定一个可复现的原因，并记录或验证针对间歇性通道关闭的修复方案。