Look at this image, in column key is Key[4-7], normal its constans, but not here.
You can see that key is deppend on 3rd packiet, called AuthLogin, ofc there is modified. First byte of those packets looks like Index of Key (?), stored key in memory. When i receive packet with same first byte as before then key is same! I mean Key bytes from [4-7] + rest 8 bytes. Also there is situation when you see first 4 bytes of Key same in much packets. But rest of Key 8 bytes is diffrent. So i think there is about 255 stored Keys, constans keys, depend on AuthPck. What you think about it?