In order to verify if EGM96 has been applied to the DEMs used in SNAP, we need a reference DEM data with accurate position and elevation. We need to know if EGM96 has been applied or not. A proper AOI should be selected as the study area.
Before we thought there could be an issue regarding the handling of EGM96 based DEM. After reviewing the code, we believe there is nothing wrong with the code.