Error while stacking the mosaic images

Hi,
I generated the temporal Sigma0 images. My study area (entire state) is falling into two S-1 products. So, I mosaic the two Sigma0 images for each date. While stacking the temporal images with the master image, the following error occurred.

INFO: org.esa.snap.python.gpf.PyOperatorSpi: Python operator ‘py_sambuca_snap_op’ registered (Python module: ‘sambuca_snap_op’, class: ‘sambuca_snap_op’, root: ‘/home/mrslabapp/saiiitb/.snap/system/modules/org-esa-sen2coral-sen2coral-inversion.jar’)
INFO: org.esa.snap.python.gpf.PyOperatorSpi: Python operator ‘S2RutOp’ registered (Python module: ‘s2_rut’, class: ‘S2RutOp’, root: ‘/home/mrslabapp/saiiitb/snap/s2tbx/modules/org-esa-snap-snap-rut.jar’)
INFO: org.esa.snap.core.gpf.operators.tooladapter.ToolAdapterIO: Initializing external tool adapters
SEVERE: org.esa.s2tbx.dataio.gdal.activator.GDALDistributionInstaller: The environment variable LD_LIBRARY_PATH does not contain the current folder ‘.’. Its value is ‘/usr/lib64/mpi/gcc/openmpi/lib64:/usr/lib64/mpi/gcc/openmpi/lib64:’.
Executing processing graph
INFO: org.hsqldb.persist.Logger: dataFileCache open start
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 23335 not equal to 23336
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
INFO: org.esa.snap.core.datamodel.Product: raster width 12370 not equal to 12371
java.io.IOException: Doppler Centroid Coefficients not found
at org.jlinda.core.SLCImage.(SLCImage.java:224)
at org.esa.s1tbx.insar.gpf.InSARStackOverview.calculateInSAROverview(InSARStackOverview.java:231)
at org.esa.s1tbx.insar.gpf.coregistration.CreateStackOp.getBaselines(CreateStackOp.java:369)
at org.esa.s1tbx.insar.gpf.coregistration.CreateStackOp.updateMetadata(CreateStackOp.java:349)
at org.esa.s1tbx.insar.gpf.coregistration.CreateStackOp.initialize(CreateStackOp.java:297)
at org.esa.snap.core.gpf.internal.OperatorContext.initializeOperator(OperatorContext.java:486)
at org.esa.snap.core.gpf.internal.OperatorContext.getTargetProduct(OperatorContext.java:273)
at org.esa.snap.core.gpf.Operator.getTargetProduct(Operator.java:387)
at org.esa.snap.core.gpf.graph.NodeContext.initTargetProduct(NodeContext.java:77)
at org.esa.snap.core.gpf.graph.GraphContext.initNodeContext(GraphContext.java:195)
at org.esa.snap.core.gpf.graph.GraphContext.initNodeContext(GraphContext.java:178)
at org.esa.snap.core.gpf.graph.GraphContext.initOutput(GraphContext.java:162)
at org.esa.snap.core.gpf.graph.GraphContext.(GraphContext.java:91)
at org.esa.snap.core.gpf.graph.GraphContext.(GraphContext.java:64)
at org.esa.snap.core.gpf.graph.GraphProcessor.executeGraph(GraphProcessor.java:128)
at org.esa.snap.core.gpf.main.DefaultCommandLineContext.executeGraph(DefaultCommandLineContext.java:86)
at org.esa.snap.core.gpf.main.CommandLineTool.executeGraph(CommandLineTool.java:534)
at org.esa.snap.core.gpf.main.CommandLineTool.runGraph(CommandLineTool.java:388)
at org.esa.snap.core.gpf.main.CommandLineTool.runGraphOrOperator(CommandLineTool.java:287)
at org.esa.snap.core.gpf.main.CommandLineTool.run(CommandLineTool.java:188)
at org.esa.snap.core.gpf.main.CommandLineTool.run(CommandLineTool.java:121)
at org.esa.snap.core.gpf.main.GPT.run(GPT.java:54)
at org.esa.snap.core.gpf.main.GPT.main(GPT.java:34)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.esa.snap.runtime.Launcher.lambda$run$0(Launcher.java:55)
at org.esa.snap.runtime.Engine.runClientCode(Engine.java:189)
at org.esa.snap.runtime.Launcher.run(Launcher.java:51)
at org.esa.snap.runtime.Launcher.main(Launcher.java:31)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.exe4j.runtime.LauncherEngine.launch(LauncherEngine.java:62)
at com.install4j.runtime.launcher.UnixLauncher.main(UnixLauncher.java:57)
done.

Error: [NodeId: WriteOp@ProductSet-Reader] Operator ‘WriteOp’: Mandatory source product (field ‘sourceProduct’) not set.

Any idea on how to get rid of this error?