BuildCraft version: 7.99.15
Forge version: forge-1.12.2-14.23.2.2619
Link to crash report or log:
Singleplayer or multiplayer: Singleplayer
Steps to reproduce: Build a Miningwell, let it hit bedrock
Additional information:

The miningwell works fine until it hits bedrock.(havn't tried lava) The green dot goes out and the red dot on the machine lits up. And it starts lagging. I talked to some helpful people on the Discord about it and with the shift+F3 command i could navigate thro the piechart to find that it's the:

"gameRenderer -> Level -> terrain_setup -> rebuildNear ->build near -> unspecified" that skyrockets.

It probably keeps mashing out chunkupdates. This causes alot of lag, that instantly disapears as soon as i remove the Miningwell. No other mods / texturepacks was used while testing this out.