Center of the basin in different place depending on the relative orbit


I am working on the topic of subsidences caused by mining tremors.

I think that my problem is interferometry related and I wonder what am I doing wrong.
I follow TOPSAR interferometry tutorial steps using bulit in graph:

  1. TOPSAR Coreg Inteferogram
  2. Topographic Phase Removal
  3. Goldstein Phase Filtering
  4. Range Doppler Terrain Correction

I have created 3 inteferograms of the same area covering (approximately) the same time scope.
Int1 - is created from S1A aquisitions - track 22 - 2016.10.08-2016.10.20,
Int2 - is created from S1A aquisitions - track 73 - 2016.10.11-2016.10.23,
Int3 - is created from S1B aquisitions - track 22 - 2016.10.14-2016.10.26.

The tremor took place in 2016.10.17 and as far as I can check the subsidence caused by it seen on all interferograms.

When I read the coordinates of the center of the basin from this inteferograms they are:
a) the same for Int1 and Int3 (different sattelites, same relative orbit)
b) different (about 250m mostly in W-E direction) for Int1 and Int2 (different relative orbits same sattelite)

What am I doing wrong ?