Was suggested to post my video here, which shows a potentially bugged reset pathing for Beldion Icewing after he was trained up in ToV. It appears as though Beldion resets and paths back, perhaps under the lava?, after being trained up towards Koi (previous trainer is killed). Beldion then unexpectedly aggros Unchainedfury in my group, who just got a fresh coth back up to Aary, and is waiting against the western wall. Beldion clearly does not path back along the route in front of Vyemm. See my youtube link below for the video.
https://www.youtube.com/watch?v=_bRynxM6hr0