For me, the main reason is lack of speed off the chest. The other day I was going for a 315 on my heavy day, I use the Westside and Metal Milita systems, and I dumped out. I had just put up 275 and 300 with ease. After I left I remembered that the 315 came off my chest too slow. The 275 and 300 were fast.
I paid more attention to my speed, keeping the heavy work and GPP all the time, but I tried something new. I don’t have a training partner so I went to the Smith machine, loaded 40% of my 1RM, let the bar touch my chest and exploded upwards. What you do is throw the bar and catch it as it comes down.
Another speed drill is blasting upwards off the pins. Set the bar at a given level, load it with 50 to 60% of your 1RM and blast. What the systems do is teach you how to outrun the bar and teach your central nervous system how to adapt to new weights.
There’s an article in here regarding static holds. Warm up. Then load 125% of your 1RM and hold it within the last 1/4 of the lift for 5-7 secs. If I remember, the article recommends not going over 140% of a 1RM. I use three holds then when I go for 225, after holding 405 in a static, that 225 goes up and down faster that Paris Hilton’s head in that video. I hope this helps. Good luck!