Terrain-Flattening - SLC to gamma0 GRD workflow

Hi there,

I’m facing an issue that I don’t get the why:

I’m applying a workflow (integrated in a gpt way using python). This workflow is Calibrating SLC datas to Beta0 and transforming it to Gamma0 thanks to the Terrain-Flattening option.

It works as expected on most of the S1 SLC scenes that I’m processing. But on some of them, there is a runtime error comming out with the error

Caused by: java.lang.ArrayIndexOutOfBoundsException: -6
	at org.esa.snap.core.datamodel.ProductData$Float.getElemDoubleAt(ProductData.java:2456)
	at org.esa.s1tbx.sar.gpf.geometric.SRGROp.computeTile(SRGROp.java:260)
	... 40 more

Error: -6
90% done. 

The process stops then at this stage:
(here S1A_IW_SLC__1SDV_20210727T102101_20210727T102128_038962_0498E1_9EE3.zip as exemple)

For each error I got, I still have a little part of the image that is well orthorectified.

What could be the reason that some product are ok for this workflow and some others not ?
S1 Metadata might be occasionally corrupted ?

Here the workflow used with fixed values as exemple:
SLC_to_GRD_fixed.xml (6.9 KB)

Another question from this concern: I automatically get no data at sea lvl when I apply Terrain Flattening, even when I set the no data at sea lvl as false… is that normal?

Thanks a lot!