Transient Simulation problem
 

Hey everybody.
I am simulating the melting of paraffin in a small capsule. The density of the solid is higher than the density of the liquid paraffin so it should sink to the bottom. This is not the problem, it works.
But:
After a while, there is no more a solid core in the capsule but a mushy phase. Not totally liquid and not totally solid. I don't understand this, because it should melt and sink down but there should me the whole time a solid core of paraffin. I compared my solution with literature and there is always a solid core until the end of the melting.
Any idea why I have NO solid core here??

Thx so much for your help!

P.S. blue = total solid, red = total liquid

I think when I set the 'Flow Stop Solid Fraction' to 1,1 the solid paraffin can sink, but the programm thinks, that this is not longer a solid material but a liquid one.
Could this be the reason why I don't have a solid core then anymore?
How can I prevent that?