For the record, I have discovered the cause of the issue: a part of the name of the file was removed by the software used to pack the file into the level. I'm in the midst of fixing the software as I type this (downloading the software to edit the software as we speak). However, here is the file that has caused so much grief, and all you need to do is put it in the Override folder and then do the sequence from meeting up with Lashowe in the Valley again.
k_pkor_las36!plt.ncs