Why does my tear trough filler always move away from the bone a few weeks after treatment?

I have had juverderm, teosyal and restylane over the years with 4 different doctors all highly qualified and very recognised. I have very deep grooves that go down to my mid face and I have very little volume in the rest of my face. I have very flat cheekbones also. For some reason the filler always moves away from the deep groves within weeks and then you can see the hollow grooves again. Any suggestions on how to prevent this? Also I have had cheek fillers to try and give my face volume