Naked short selling is the problem. This is what retail investors are attacking.
Investment houses can sell unlimited amount of stock depressing the price of a companies stock to the point of BK.
There is no requirement to return borrowed stock within a month, because no stock has been borrowed.
Ahhhhh, but therein lies their conundrum. They, on paper though not in practice, are not naked, rather the houses that allowed the trades invented the stock out of whole cloth and are charging them sky high interest. All of this done on a wink and a nod. Wall Street is crooks to the left and thieves to the right with fraudsters in the back and liars up front.