When I select a label, and "select all N messages in X label", all possible labels are partially selected. To be clear, this doesn't happen unless I select all messages in a label. None of the messages selected have any other label; to put it another way, each message has only one label, the one with the full check, and no others.
If I just select all messages on the page, I don't have this problem.
I've manually deselected all the tags to wipe the messages, and when they're reselected, none of them are partially selected again.
Aside from the obvious question, "why?", is there a way to fix this without manually deselecting a bunch of tags?