Might not apply for that heavy of weight because I can't move that around unless squatting/deadlifting.
BUT! When I was plateau'd at 225, what worked for me was high rep over training until complete and utter failure. Before I got to the "burn out," I'd lift 80-90% of my max and do 3-5 second slow, tight controlled negatives, pause (just above chest, not touching) then explode through (if I even could. Obviously so your warm ups and don't just hit 80% first lift