ABAQUS/Explicit Field output huge fluctuations

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I'm using ABAQUS Explicit, simulating a dynamic pressure load within a confined box. I tried outputting the Mises stress at the inner corner node, and the output I'm getting has these huge vibrations (as attached). I'm not sure what this is, it's probably something to do with finite element mathematical stuff, but can someone enlighten me?

 

[crustaccione]

I forgot to mention, I'm using Dynamic/Explicit, NLGeom ON, in case this is important information.