Why topography effect remains after topographic phase removal is applied?

Hi all
I want to extract deformation data from my interferogram.
As you know after generation of interferogram we should remove topographic phase using topographic phase removal operator.
This process was done for a full frame of asar ims product with orbit interpolation degree parameter (3)
but topography phase effect remains yet.
It is mentioned that precise orbit file were applied to product.
What could be the reason of problem?
Have you ever faced with such a problem?
Thank you for your attention

See Wrongly removed topo-phase in differential phase?!