If you set a large port number, such as 55222, as a send port of the SFTP adapter, the host instance that runs the port logs the following exception in the Application event log:
System.ArgumentException: Port number cannot be negative
The fix that resolves this issue is included in the following update for BizTalk Server:
Cumulative Update 5 for BizTalk Server 2016
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.