This is probably impossible to fix since this is a problem with the rendering engine.
In the rendering engine, objects are drawn separately. When handling transparent objects, the engine needs to determine which object is closer to the camera. Then it draws them in order, alpha blending with the objects behind it.
This method fails when such ordering cant be done, for example in the case of two arches where both can be occoluded by each other.
In here, this is probably the case and its a problem in the engine, a problem badspot probably cant fix.