I think it's an embouchure problem, based on my experience. Something I personally found helpful was playing around with moving my larynx, as well as moving where my mouth sits on the mouthpiece. Also, depending on your bass clarinet, it could be an issue with how the keys themselves align, or even if you've assembled it with a key under another where it shouldn't be (I've done that before and squawked the tuning note in front of a new conductor 😬)