When I am running my own events in SLIC from a macro, for small numbers of events (3k) the distribution looks ok. However, when I run something a bit larger like 100k events, I keep getting strange checkered patterns. I've been setting a /random/seed number for different runs, but this seems to have no effect (using this vs not using this and setting it at different values). 

I am attaching a photo of what the cosmic run looks like.  While the underlying events look good, there is a very distinct pattern that I need to get rid of. I also see this same pattern if I shoot electrons at the ECal. Any suggestions would be very useful. 

I am wondering if GEANT4 is using the TRandom random number generator? I know there are errors with this. I am not sure what is being used with the SLIC interface. 
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