There are a tests implemented in the s1tbx-op-sar-processing module named TestDEM and TestDEM2.
They sometimes fail on latest Linux distros like Ubuntu 20.04.
But it seems not only related to the Linux version.
During the test DEM data is downloaded. Then the elevation is requested for certain pixels. This sometimes fails.
Deleting the downloaded DEM and redownloading it with the next test execution the test works.
But it doesn't seem that the downloaded file is corrupted.
Till now only observed in latest Linux distros like Ubuntu 20.04. Not seen yet on Windows