Missing button presses (or, in this case, releases) is generally due to irq latency - however, we've not seen this problem since about beta2, when the kernel was tweaked to eliminate this problem. It's definitely not anything new introduced in beta9 - the code hasn't changed since before first customer shipping in August.

So no, it's not a known problem and we've not seen it here, which makes it hard to "fix" for the 9b release.

Hugo