There is a Newdark bug in this mission, but it only partially affects the game play. In the caves where you need to cross the beam, the moving platform in Olddark reached to the top of the ceiling preventing you climbing onto it, but with playing with Newdark you can climb onto it making that puzzle rather too easy to mange.

However Voodoo has supplied a .dml fix for this issue that is available here:
http://www.ttlg.com/forums/showthread.php?t=145374

Warning: DO NOT install the dml fix directly into your main Thief folder, rather install it into your FMsel/FMs/treasury root folder