Druid Greenmask of Willowgrove can not be used with Symbol of the Ancients

[Glyph]

Sometimes when I equip my Greenmask of Willowgrove it un-equips my complete Symbol of the Ancients. Think it has something to do with the Disguise feature. If I try to equip the ring with the mask on it says I am unable to use this item. Happens often when wildshaping.