The question

In the process of selling home, and after the due diligence period, the buyers put a stop payment on the deposit check because they were wanting to more money. Sellers said no. Ultimately, title company alerted Sellers Agent, who was unaware of this situation. This is a buy/sell transaction for the realtor. But, realtor signed contract with Buyers in this situation NOT the sellers. What are the legal ramifications on putting a stop payment on a check when buyers were outside the due diligence period and in serious breach of contract?