Hi David.
Eric may be right.
I have the 10". Check/tighten the screws that fix the upper and lower cylinders to the cast metal rims. I felt some movement when lifting from the trusses on mine. There's 6 screws per rim, 4 rims. Top rim will not be the cause. My instructions say to carry the scope by the trusses, this may cause some movement. I carry mine by grabbing the large aluminium alt pivots.
Hope this helps.
Regards
Richard