When rolling out new servers for Remote Desktop Services in Windows Server 2016, that are load balanced with F5 (Connection Broker servers specifically), I found that the Send/Receive strings used for the Health Monitors in F5 that we used for Windows Server 2012 R2 did not work in Windows Server 2016. After diving into some diagnostics logs, it looks like the response string has changed in Windows Server 2016.
Here are the Send/Receive strings for both the old 20012 R2 and the new 2016 that worked for me: