So I've been diving into the most recent stable version of the Billionaire Skyblock modpack for 1.12.2 (instance info says using mod "Ancient Warfare Core 1.12.2-2.7.0.772"), and I set the quarry up on my good old in world water and lava style cobble generator, with a bound of 1x1x1 and later with 2x1x1 and 3x1x1 setups, and it works perfectly if I click each time a new block spawns in. however if I keep the shift + right click held down, it will break blocks much faster and once there are no blocks to break, it's loop breaks out of the height bound of 1, and at that point it quarries through the bottom of my island and, as best I can tell, endlessly starts trying to break air blocks further and further down into the void, I literally have to break the quarry and set it up new again to get it back in bounds and working again. I haven't used it with an automated power source (i.e. watermill), mainly because I don't yet have the materials to build one, so I have no idea how that would work, but I suspect it'd break out right away. ...ok, nix that, I went into creative and gave myself a waterwheel generator, it only supplies enough torque to break one or two blocks before new ones form so it can't break with at least a 2x1x1 setup, but manually powering it really shouldn't produce so much power as to break it either. I will post this issue on the modpack's support page as well if I can find it, but since it broke without any other mod's items in use, it might be broken in this mod itself.

*I was using a simple wooden hammer when manually powering the quarry