Here follows the crash report:

http://pastebin.com/2mEHg7Xk

This is not everytime, but, sometimes, crashes...

Can you reproduce without Cauldron? Looks fine to me.

Similar bug exists with filler. Cauldron as well.
Crash report

Player said that he placed filler, tried to select mode and server crashed. And every time he tried to login, server crashed.
I couldn't reproduce it myself even at the same coordinates and on the same server

Same issue. Can reproduce both on a Cauldron MP server and in single player with the same modpack. In MP it effectively kills the server as any player wandering within range will be stuck in a crash loop.

http://pastebin.com/Z7Z058gD

Place 3 land marks in an L shape. Place a quarry next to one of them. Place a chest and a power source. Quarry will build the first corner of the frame and then crash when it gets to the top. Save is effectively corrupted.

Edited to add. In fact I get the same with 4 land marks in a rectangle. When you place the quarry, you don't get a full frame, just one short stub. Powering that quarry will corrupt the save and kill the server.

@Deadlock989 - how are you reproducing it?

@EverNife @Deadlock989 please try http://asie.pl/bc7021a.jar

Same result. Quarry placed with no land marks works, putting a default size frame. Any quarry placed next to a landmark produces just one short stub which will crash server and corrupt save.

Same here :D