Reload Unifi OS Without Reboot

NOTE: As of Unifi OS v2.5.17 the podman command no longer works on UDM Pro devices. It may not work on any devices with the newer Unifi OS installed.

You can try this command to restart just the UniFi Network application.

systemctl restart unifi

Restart OS - To do this, SSH into device (see this article) and run 
podman restart unifi-os
This will restart the UniFi Applications and Remote Management Service. Routing, VPN, and other network functions should continue to operate without any interruptions.

The web interface on the Unifi controller was no longer responding and the CPU usage was way too high so I knew I needed to restart something but I could not take the main internet connection offline. Running this command fixed the immediate problem.