Board Thread:Skyrim/@comment-10199795-20130531120916/@comment-6881629-20151018110556

Never heard of it happening to Lydia's armor but Serana's hood does sometimes duplicate when she equips it, on PC you can open the console click on her so shes targeted and use the command -

showinventory

To view a list of her inventory and see how many hoods she has, then use the command (change the 1 for the number of hoods to remove and the XX to the load order of your Dawnguard) -

removeitem XX00E6A0 1

The unofficial Dawnguard patch stops it happening, i'm afarid i don't know of anyway to fix it on a console.