After you upgrade to Cumulative Update 7 (CU7) for BizTalk Server 2016, the SFTP receive location stops polling intermittently and never recovers until the host instance is restarted. There is no error entry or warning in the event logs, and the receive location is not disabled.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This problem is fixed in the following cumulative update for BizTalk Server:
Cumulative Update 8 for BizTalk Server 2016
For information about the service packs and cumulative update list for BizTalk Server, see the following article in the Microsoft Knowledge Base:
2555976 Service pack and cumulative update list for BizTalk Server
For more information about BizTalk Server hotfixes, see the following article in the Microsoft Knowledge Base:
2003907 Information about BizTalk hotfixes and Cumulative Update support