Have you considered removing the band? I know there are reasons for keeping them on, but I have heard many stories about them getting snagged on things etc. I am wondering what metal the band is made out of...Some metal will oxidize and rub off on objects. You should definitely investigate this further, but I just keep thinking about how certain metals have turned my fingers grey or green (cheap rings etc).
Side-note: if your bird ever "mouths" the band, that could be bad if it isn't stainless steel or aluminum, as other metals can poison birds when ingested in small quantities.
I saw that hormones were discussed and I don't know if that relates to the leg at all, but just because it was mentioned, DO stick to petting only on the head and remove access to any boxes, huts, tents, holes, low-ledges, bedding, undersides of furniture, cave-like spaces and shadowy areas. Birds and shadowy spaces are inclined to nest and nesting birds are hormonal birds.