GPT command not ending


I am trying to run Oil Spill detection on Sentinel 1 data products. I have created a graph file in SNAP and I’m using GPT to process data products on a remote server. The machine is a poweredge R510 with 64gb of ram and two Intel Xeon E5620 CPU’s running Ubuntu Server 16.04. When I try process the data it outputs the data OK, but GPT process doesn’t end and seems to rewrite the Sigma0_VH.img and Sigma0_VV.img files every hour or so. Is there something I’m doing wrong. The test data is and I have included a link to the graph file below.

I get the same trouble with an intensity processing over certain scene (SNAP 5.0 + S1TBX5.0.1), ex : 20160415T172304_20160415T172331_010835_01035A.