I noticed this when I built my arena deck today; it has 'not a number' (NaN) for my arena deck rank. I waited to report it to see if it would get any plays, and apparently it still is getting plays. I don't know what's causing it, though. I do know my brother has NaN for his arena deck ranking as well, but he hasn't built an arena deck in a long time, so I figured it was just expired for him. This is the first time I've seen it for myself, and I haven't seen it when playing vs the arena.
