Bug? Killing Zhurlong costs five reputation points

Good afternoon,

I just started playing Bladur's Gate after buying it on gog.com. As per their recommendation, I installed both Baldur's Gate II Fixpack and Baldur's Gate Trilogy-WeiDU 1.18.

According to every guide and walkthrough out there, you can kill Zhurlong the dwarf after returning his boots, without your reputation decreasing. However, every time I do so, I lost five reputation points.