Yeah, I've had this before with pressing and squatting after injuries. Go through the rehab, get everything working again properly and then get to a heavy set and the same thing you're having happens. Went away fairly quickly. Part of it was getting the motor patterns back and the other part was just not being under the bar with significant weight on it for a while. Being under heavy DBs and being under a heavy BB are a little different. Give it a little time.
The other thing to try is right before your lift to visualize yourself going through the movement with the same speed and power you did in your earlier sets. Even move through without a bar in your hands. Then go for it. Sometimes all you need is a little Jedi mind trick to make it fly.