Well, I was pretty heavily involved in the beta testing for the game way back when. The NWN1 PW builders were invited to test the software quite extensively, including both the client and toolset for building.
There were quite a few issues reported which were not addressed (and still are not addressed today), which is part of the reason why I've moved on to different games.
About 90% of the major issues with the game were caused by using a dated graphics engine, and then the subsequent "modifications" to said engine which were not, in any way, optimized.
Not being a graphical engine coder, I cannot begin to describe what might have gone wrong, but I can say that most of the hooks built into the game for modificaiton did not work properly at release. How the propretary stuff worked then brings the question, "how did they get it to work".
I believe there were a lot of "workarounds" with the base release which still exist to this day, but again, I can't see the source code.