Watch that finger placement...
...particularly your right ring finger. Doing "finger drills" (holding the instrument and running your fingers up and down the tone holes, without blowing but holding it in place) will help.
Clarinet playing has always gone for a "falling finger" approach to closing off the finger holes, as opposed to the saxophone practice of pushing the buttons. Both are much the same as far as gross finger movements are concerned, but the clarinet approach pays more attention to the pad-like "seal" against the tone hole chimney.
If you are furnished with "fat hands" (as am I), this isn't as much of a problem. Your broad fingers automatically provide a broad, fleshy sealing surface. However, then you have what I call the "angular problem", whereby fitting so much hand into such a limited space (where the first finger has to be in one specific location, the third in another, and the fourth finger has to move around a four-key cluster) can cause difficulties with laying the fingers down so that everything fits while at the same time the "flat" portion of the right hand ring finger properly falls over the chimney. In particular, shifting the little finger from B natural to Eb can cause the other fingers to "roll" and lift ever so slightly from the tone hole chimney. Result: instant squeak, as you have (in effect) opened an additional register key on the instrument.
The first problem (pushing instead of falling) can cause a squawk from any of the right hand fingers. The second (which amounts to a twisting of the ring finger) can make the transitions through the break from B natural on up to Eb problematic.
(I have never encountered a similar problem with the left hand, despite the greater range of motion with the little finger. I think this is because there is no "bunching" of the hand during the effort to reach a key located in a similar fashion to the Eb key.)
(Also, the problem is not encountered in the lower register, probably because the lips are able to keep that portion of the horn better under control.)
Sometimes, moving the thumb rest can help. The Series 9 didn't come with such an animal, and not all aftermarket rests are particularly robust. (My repairman refused to install them, saying categorically that none of the commercial versions measure up to his standards. (Marvin is pretty picky, although he does like to listen to Rush Limbaugh.)