TerraSAR-X interferometry Poor Result

Hi all
So I’ve been trying to create interferogram of a pair of Terra SAR-X SSC StripMap level 1-B data.
I follow procedure from Sentinel-1 StripMap intereferometry processing from here http://step.esa.int/docs/tutorials/S1TBX%20Stripmap%20Interferometry%20with%20Sentinel-1%20Tutorial.pdf

below is screenshot of TerraSAR-X image pair and baseline information from SNAP stack overview:

As you can notice it seems like there is a significant intensity differences between July 11,2018 data and July 22,2018 data

Coregistration result using default parameter:

Interferogram and coherence after subset:

unwrapped phase:

I’m out of idea how to improve the result, maybe someone could give me suggestions, I really appreciate it.