Same thing here. I could ALWAYS grab and drag under any condition and then toss a window to the top and it would cascade in to fill the monitor. OR toss to the right or left and it would take half the monitor. All of a sudden that convenience just stopped. Maximized windows are locked in place and you have to use the middle icon to make it smaller then reposition then click maximize to fill the window again. It had to be an update that took this great convenience away.
My friend, Just go to the settings - System- multitasking and enable Snap Windows