I caught the front edge of my snowboard in December and fell face down hard. My mid-back felt like someone tried to break me in half. Since then, if I don't squeeze my abs really fucking hard I feel that mid back twinge or pinch. It doesn't hurt but it's definitely not normal. I think I might have done some damage. Doesn't hurt deadlifting/squatting or on a daily basis, just during press if I don't squeeze hard.
One that helps for me during press is to think of being a transformer right before I start pressing the first rep. I visualize my legs being steel and from my feet to my shoulders it locks in place, making me squeeze really fucking hard everywhere. The press makes me the most tired out of all my lifts by far.
Another thing I do other than squeezing my abs tight is I tuck my pelvis in before each rep. Hard to explain but it feels like "showing your crotch to the mirror" in front of you. It straightens the low back a bit and if you squeeze while holding that tuck, it also helps with the mid back pinch. (A coach told me this).
Hope this helps.