Running Minecraft 1.10.2, Forge 12.18.3.2185, Mekanism 9.2.1.298

1. Install LevelUp! mod.
2. Acquire an Atomic Disassembler.
3. Level up and assign points to woodcutting skill.
4. Switch Atomic Disassembler to Vein mode.
5. Break a wood block in a tree.

All of the connected wood blocks should break, but only the clicked block will break.

Note that another mod, VeinMiner works as expected:

1. Install VeinMiner.
2. Acquire any axe.
3. Level up and assign points to woodcutting skill.
4. Break a wood block in a tree with VeinMiner active.

This will correctly break all of the wood blocks in the tree (plus, any bonuses from woodcutting skill will be applied).

Not totally sure why this would be occurring, but clearly LevelUp! is interfering with some low-level MC functionality. I'm going to leave things be.