Cancelled Loads

Do you lately come across cancelled loads that already had confirmed rates? It seems within a month, four loads got cancelled. One looked like it was from the customer while I was there already for pick up. I didn't charge anything for it just to keep a relationship with a new broker who I served in the past, just lost a few hours that day getting to the shipper. I had a precooled trailer. It didn't seem that the broker was notified in time. So, I believe it was out of control.
But I had other loads that had confirmed rates and cancelled at the end of the day or next day. I am not sure if they sold the loads to someone else. It just seems weird. I didn't experience it before but for the past four weeks or so.
One load even showed up on the DAT board after they cancelled.
Not sure what is going on. If I am targeted by brokers, or I'm setting accounts with brokers who are not trustworthy.
Any brokers you know that are doing that? If you know brokers who are constantly cancelling the loads once booked, let me know. So, I won't go through the trouble setting accounts with them.