F5 Monitor tcp_half_open is getting down error Ipv4 address mismatch

This KB may help: https://support.f5.com/csp/article/K12829

-It is an older KB that is no longer maintained.

--I hope this helps! Have a great day!

Workaround

To work around this issue, you can remove the TCP half open monitor from the pool or node and then add the monitor back. To do so, perform the following procedure:

Note: This workaround may need to be performed following each system reboot.

1. Log in to the Configuration utility.
2. Navigate to Local Traffic > Pools or Nodes.
3. Click the appropriate pool or node object.
4. Remove the TCP half open monitor.
5. Click Update.
6. Re-add the monitor to the pool or node object.
7. Click Update.