The difference in the size of the interferograms of the same area

Hi, all!

With the help of ESA SNAP received a temporary series of interferograms according to the Sentinel-1A for a specific region. Coordinates region is set the same for all interferograms. Why the size of the interferograms after subsetting, in pixels differ (no more than 1-2 pixels in height)? Geographic coordinates of areas at the same match.

Thanks for the reply.

Could you explain further how to reproduce the problem?