The thighs tend to adduct due to weak abductors, meaning your glutes are weak or extremely fatigued, but most likely the former. You need to get those glutes up to par, especially the gluteus medius. Maybe you should incorporate unilateral work in some workouts such as lunges and Bulgarian squats.
Oh, I would also highly suggest adding in dynamic warmups for your legs and glute activation exercises to get them firing properly, if they are not already.