When you're in the bottom position, from this side view, your forearms are vertical and some reps have them angled slightly towards your feet. Just like in the press, your forearms should be pointing back to the lockout position.
On your next bench workout, try 2-3ct paused reps during your warm ups, and make sure that your forearms are angled back toward lockout. Obviously, record and watch the warm up to make sure that you're doing this. See if this helps your work sets.