shadowRenderPass and the backside of a cloth

I have a problem with the shadows in my standardgame, most shadows display correct now accept for 1 on a flag.

the front is oke but the backside is all grey now.



My shadowPass uses additive  and the settings are:

      shadowPass.blended.setDstFunction(AlphaState.SB_ONE);
      shadowPass.blended.setSrcFunction(AlphaState.SB_ONE);
      shadowPass.blendTex.setSrcFunction(AlphaState.SB_SRC_ALPHA);
      shadowPass.blendTex.setDstFunction(AlphaState.SB_DST_COLOR);


this is basically the only way i can get proper shadows for the rest.

anything i can do fix the backside of the flag ?

Thx
Hellmaster.