Closed Loop Speed mixed mode - mixing sources of motor commands

Hope this one's easy (and i'm overlooking something obvious). I seem to be unable to set motor speed (RPM) using !S _S via microbasic for Propulsion (motor command 1) while Rotation is being commanded via a pulse input. I try _S, _M, _G (believe _S is what documentation calls for in closed loop speed). If I configure command 1 as another pulse input she goes. if I try to tell her to go via script while steering via pulse, she steers but she no wanna go! Any ideas?