I'm not certain what is causing the spinning, but I can tell you what I would do to troubleshoot it. First, make sure you click "control from here" on the command module. Second, since the RCS thrusters on the lander aren't aligned with those on the command module, I would disable them all (right click "disable rcs port"). And third, I would put the brakes on (click the brake icon at the top of the screen). There may be no merit to putting the brakes on, but I hate seeing wheels spinning and thinking it may be turning my lander somehow. And then if you need to kill rotation, you can always accelerate time and it will freeze your craft in position. Hope this helps.