Well, I am officially stumped on that last one.
I agree the PLM(00) responder link is missing, but it shouldn't be necessary. The link is added during the "link to interface" routine for i2cs objects. A device needs one responder link in its database before it will respond to commands from a device. The 00 is literally a throw away link as no such group exists or can exist. So MH creates it first during a psuedo-manual linking session, and then ignores it forever.
I don't know how you got where you are, not your fault I have seen this happen to me too, but having the A1 responder link should be all you need. I have a number of devices lacking the 00 group that don't have any issues.
All I can suggest is to wait a bit and see if it clears itself up. If not you can try turning the offending device on and off. Just pull the air gap. This will cause you to have to run scan links on that device again, but it might resolve it.
Beyond that, my next step would be a factory reset of that device, sorry.