I agree with you that I am seeing little that makes sense here. I have only seen a sell off like this when there is an imminent bankruptcy or fraud is identified.
Searching Armistice and you are right they have an interesting recent past with biotech including allegations of insider trading and dumping shares. Seems wild though they invested millions only to almost immediately dump at big losses. Does not make sense unless they came across information shortly after the placement that was not caught during reviews before the placement.