Possible reason;
Companies sometimes declare bankruptcy with little warning. Other times, there is a slow fade to the end. A short seller who didn’t buy back the stock before trading stopped may have to wait until the company is liquidated to take a profit.
However, the short seller owes nothing. That is the best possible scenario for a short seller. Eventually, the broker will declare a total loss on the loaned stock. At that point, the broker cancels the short seller’s debt and returns all collateral.