With the release of BizTalk Server 2016 CU5, there is an important upgrade of WinSCP as mentioned in the release notes of KB4087345:
BizTalk Server SFTP adapter is updated to use WinSCP version 5.13.1.
This means you will want to upgrade WinSCP to version 5.13.1 on all of your BizTalk servers if you are using SFTP that is, or are planning to use it at some point.
To do so, you must update the DLLs installed in your BizTalk Server installation directory (default C:\Program Files (x86)\Microsoft BizTalk Server 2016\).
Now, for CU5 I made another change to include the correct version.
You can find the adapter script (originally from Thomas Canter) here, I only updated references to the correct version for BizTalk 2016 CU5: