Why do some entries in router's client list have 'N/A' instead of a MAC address?

In the client list of my ctrld service (running on OPNsense router) there are sometimes clients that have 'N/A' instead of a MAC address.

They seem to only operate like that for a short time (minutes) before eventually ctrld detects their MAC address and properly assigns their traffic to one of my defined clients - but why? It causes them to briefly receive the wrong ControlD profile and get the wrong access, and creates unwanted entries in the router's client list.

I'm now using the most recent pre-release build and manually specifying assignment of individual MAC addresses to specific ControlD profiles, because I haven't otherwise been able to get devices to reliably assign to their profiles when they're on the local network.