Ok i found the cause of the problem, it would appear setting hlsl_prescale_x & hlsl_prescale_y in the HLSL settings to 5 is the cause of the issue with GroovyMame, anything over 3 causes issues!. This is strange as in ManeUI64 the exact same setting allows me to have hlsl_prescale_x & hlsl_prescale_y settings at 5 without any issues??