Found in Version:
tr_dres_bug_small_vo.nif bounding box should be smaller/resized.
tr_swampfly_vo.nif tends to disappear under the Bal Oyra fort floor, making impossible to kill it and finish the related quest (e.g. if paralyzed, this happens every time if a MCA guard is near) .
Possible things I’d try is changing the Bounding Box to be more similar to the one used e.g. with CliffRacer.nif, covering the flying creature legs and a little below. and/or put some collision box under the fort floor