GPU sagging occurs when the graphics card is too heavy for the case bracket or PCB to support, usually caused the massive cooler shrouds. Here are some ways to combat this.
Graphics processing units (better known as GPUs) have grown considerably in size, way past the limit that was expected of this plug-in cards. Should you pick up a new GTX 1080 or RX 480 graphics card, you may notice what is called "GPU sagging." This is when the surrounding cooling shroud and solution is too heavy for the PCB and supporting case bracket to uphold. Thus the card bends a little.
Full story from the WindowsCentral blog...