Try out these few constraints, I don't understand NGDBuild allows space in the LOC while not in the signal name.
NET "out_bus( 9 )" LOC = " AA2 "; NET "out_bus( 8 )" LOC = " C2 "; NET "out_bus( 0 )" LOC = " D2 ";
NET "out_sig " LOC = " B2 "; NET "out_sig_1 " LOC = " A2 "; Kelvin