Berengar's Sword quest bug.
PC, Patch 1.10 + Hearts of Stone, NG+, no mods, Kaer Morhen before Battle of Kaer Morhen quest.
After defeating the Chort i have to look for a silver sword, which appears to be in a bag in a corner of the cave, but when i walk up to it using the witcher sense i can clearly see the bag glowing red, but at about 3-5m distance it just vanishes into thin air. (my guess the same bug makes the crystal in the ancient watchtower disappear for the wolven gear quest)
screenshots:
http://imgur.com/a/MToM6
oh and for some reason there are almost exclusively berserkers now in kaer morhen which near instantly respawn, no harpies at the ancient watchtower for example.