Postmfix not printing all data

I am using postmfix to extract pressure data from a 20 second simulation but postmfix wont print the data from 16 to 20 seconds for some reason. Using paraview to examine the same location, the data exists and the pressure is changing over that time chunk but the postmfix report keeps coming up blank for that location and time period. Any help?

How large are the SPx files? I think I remember there being an issue when files exceeded 2GB.