Odd behaviour - VSTi preset browser/filter

There’s something not right with the presets browsing. Hard to explain because the symptoms vary somewhat but I’m finding with the browsing filter active very strange things happen, often entire columns under say ‘catagory’ or ‘sub catagory’ just vanish, or remnants of a previous list of items from a previous selection get left behind even though a new catagory is selected. I’ve attached a couple of screen shots which I hope will help better explain what I mean: