Sentinal Terrain Correction

I am trying to perform Range Doppler Terrain Correction on Sentinal data but I am getting following error on my server PC. However same procedure is working fine on another PC. What could be the possible reason?

java.lang.IllegalStateException: There is already an image reader.
at org.esa.snap.dataio.geotiff.GeoTiffProductReader.readProductNodesImpl(GeoTiffProductReader.java:108)
at org.esa.snap.core.dataio.AbstractProductReader.readProductNodes(AbstractProductReader.java:178)
at org.esa.snap.core.dataop.dem.ElevationFile.getLocalFile(ElevationFile.java:138)
at org.esa.snap.core.dataop.dem.ElevationFile.getFile(ElevationFile.java:106)
at org.esa.snap.core.dataop.dem.ElevationFile.getTile(ElevationFile.java:83)
at org.esa.snap.core.dataop.dem.BaseElevationModel.getSamples(BaseElevationModel.java:161)
at org.esa.snap.core.dataop.resamp.BilinearInterpolationResampling.resample(BilinearInterpolationResampling.java:82)
at org.esa.snap.core.dataop.dem.BaseElevationModel.getElevation(BaseElevationModel.java:99)
at org.esa.snap.dem.dataio.DEMFactory.getLocalDEM(DEMFactory.java:182)
at org.esa.s1tbx.sar.gpf.geometric.RangeDopplerGeocodingOp.computeTileStack(RangeDopplerGeocodingOp.java:861)
Caused: org.esa.snap.core.gpf.OperatorException: There is already an image reader.
at org.esa.snap.engine_utilities.gpf.OperatorUtils.catchOperatorException(OperatorUtils.java:440)
at org.esa.s1tbx.sar.gpf.geometric.RangeDopplerGeocodingOp.computeTileStack(RangeDopplerGeocodingOp.java:1067)
at org.esa.snap.core.gpf.internal.OperatorImageTileStack.computeRect(OperatorImageTileStack.java:122)
at org.esa.snap.core.gpf.internal.OperatorImageTileStack.computeTile(OperatorImageTileStack.java:86)
at com.sun.media.jai.util.SunTileScheduler.scheduleTile(Unknown Source)
at javax.media.jai.OpImage.getTile(Unknown Source)
at javax.media.jai.PlanarImage.getData(Unknown Source)
at com.bc.ceres.glevel.MultiLevelImage.getData(MultiLevelImage.java:64)
at org.esa.snap.core.gpf.internal.OperatorContext.getSourceTile(OperatorContext.java:449)
at org.esa.snap.core.gpf.internal.OperatorContext.getSourceTile(OperatorContext.java:435)
at org.esa.snap.core.gpf.internal.OperatorImage.computeRect(OperatorImage.java:75)
[catch] at javax.media.jai.SourcelessOpImage.computeTile(Unknown Source)
at com.sun.media.jai.util.SunTileScheduler.scheduleTile(Unknown Source)
at javax.media.jai.OpImage.getTile(Unknown Source)
at com.sun.media.jai.util.RequestJob.compute(Unknown Source)
at com.sun.media.jai.util.WorkerThread.run(Unknown Source)

are you using the latest version of SNAP including all updates?
There were problems with the SRTM 3Sec data source lately which have been fixed with the last update.

You can also test SRTM 1Sec (AutoDownload) as an alternative. The fact that it works on one computer but fails on another indicates a problem in the configuration