What is the recommended solution for the issue of black blocks in the middle of terrain-flattened Sentinel-1 images? Excessive multilooking is not a solution. I have tested 5m resolution DEMs with ‘non-regrid’ which fails with null pointer exception. There is no change with version 6.0. I am working with S1A_IW_GRDH_1SSV_20160526T194932_20160526T195003_011434_011670_F15D
Additional information: The minimal process is read-calibration-terrainflatten-write. Using various downloaded, or my DEM achieves a similar result. DEMs do not have zeros or fill values. 10 of the 47 S1A, relative orbit 162, images over the mountains near Port Moresby, have large black blocks in the same or similar areas of the terrain-flattened images. Most of the others have no defects, except a few that contain much smaller defects near shadow areas. Below is a small subset of the 20160526 flattened image.