[Darren69]

I just noticed you said 100 miles on new plates so its unlikely to be that they are tanged, basket maybe. Did you check the pack height when you fitted new plates? If its too high it can drag slightly which can give strange squawking noises.

Is the dished plate installed right way around in the right place? I'm just "clutching" at straws really! But it doesn't sound serious if its working ok and goes away, it might just be bedding in.