I have a problem when doing interferogram formation,
This happened with me, but it was because that area had water. Interferogram cannot form over water. I think area on the right might be water (Sea, lake, river, etc.) that’s why it is like that. You can do terrain correction and confirm that.
the stripes on the right and left side are introduced by SNAP, for example when there are pixels which are not covered by both images (no phase difference can be calculated).
This is not a problem as you see in the following examples.
The stripes can be tackled by creating a subset: DEM generation with Sentinel-1 (Figure 20)
But you can also simply ignore it and have it in the final product: