Double glazing leaded lights damage

[gjc]

I have BAC upvc replacement windows with Tudor style(criss cross, diamond shape)leaded lights. These are made up of strips of lead about 7mm wide stuck on the outside of the glass. The windows are about 15 years old. Two or three sections of the lead are peeling off. Looking more closely, it would appear that at the junctions where one lead strip is crossed on top of another, the top strips are starting to buckle, probably due to expansion or flowing. The few that have peeled seem to have broken at this buckling point. this is all cosmetic and does not affect the workings of the window in any way.

Does anyone know what is happening and the best way to stop it getting worse, and to repair the ones that have peeled. Thanks in advance.