I'm back. I think there is a bug with the buttons in the title screen were they will sometimes sense that you are hovering your mouse over them while you are hovering your mouse over the button just below them.
Welcome back. I think that bug might be caused by the fact, that buttons which increase their size when selected, also increase their bounding boxes. So if you select different button, but your cursor is still on a button that got scaled up, the game will sense that you are still hovering on that previous button. That however will be fixed, since I'm planning to rework the main menu.
As for the zombies getting stuck on dirt piles (actually they're sandbags), this is due to their code not really being optimized for pathfinding. Though I'm planning to rework mobs' code, and to implement proper pathfinding after that.