The first time I modify the land counts for dual lands in a deck with the + button, it seems to work. But if I re-enter the deck, I get the following bugs:

In the deckbuilder, using the deck layout in the screenshot, I can remove dual colored lands and double faced Pathways with the - button, but the + button is greyed out. It will not allow me to add more of those dual colored lands, even though I own those lands, with the + button.