That will become more common from here on out. Just remember "the first rep is a lie!" and not let it get into your head for the remaining reps.
Before you do that, watch this —
Press and Bench Press Programming – Getting and Staying Unstuck. You're getting into that range where your press is going to stall. It does for all of us. Give that 120x3x5 one more try, but make sure that you sleep and eat very well going into it, perhaps even extending your rest period a minute or so. If it sticks again, start following Nick's guidance that he lays out in the video.