Shuttle yaws before SRB cutoff

[GoSlash27]

So I'm playing with my replica space shuttle, the K.S.S. Konstitution. I've got it pretty well tweaked for the initial climbout and roll maneuver, but it goes squirrely just before SRB burnout. The odd part is it *yaws* radically to the right.

Any ideas what might cause this behavior?

Pics:

All good.

All very not good.

Best,

-Slashy

[FancyMouse]

May need some more tests. Does it repro if you don't control and simply let it go straight up? What if it's launched in different orientations? And turn on F12 in case aero arrows give some info.

[Lindy]

Do you have anything in the cargo bay with a bit of asymmetric weight distribution, or anything on the outside causing asymmetric drag?

[NathanKell]

Joints are still very wobbly in KSP, especially a light part between a heavy SRB and heavy tank. My guess is the thrust from the SRB causes the decoupler's joints to wobble.