I have an atlas in QGIS 2.14 with a filtered legend whose position is anchored at the bottom right corner. When viewing atlas pages individually within the print composer, the legend size increases with number of items on each map, but does not decrease when the number of legend items is reduced on subsequent pages. On export, the legend box is at the same maximum size on all pages, leaving a gap under the item list where there are less visible layers. I don't remember having this problem in previous versions - is this a bug in 2.14?
Edit: I have logged this as a bug - issue 14707.