So i've finished this quest a while ago, but not without bugs.
The bug is with some creatures wraiths, spectres, vampiress. some undead that rob you of your xp and are blurred.
The problem with then is that for some the script is turned off and they keep standing not fighting back.
Another problem (the most anoying one) is that some are simply invisible. They do not fight, nor move, and are simply standing still blocking the way for some areas in some cases.
I did not had Cuchoinete in my group while i did this quest.