As Shanim ,

The problem is simple. The refraction index and translucency are too low.  Where mesh densities change  or one ends and another begains the SSS is calculated at ratios to match. Also Carrara is funny lower numbers in some setting boxes actually make things stronger. A little SSS goes a long way.  Objects do not have to be solid or continuos to get proper SSS but the settings are variable according to light and object size. 

Here are a few  picture examples of my SSS setings.  I am using the same 3 point light in all 3 renders. One indirect in front 70%white a bulb in front on the floor golden 55% and a blue bulb back light at %70.