When running in batch mode with pvpython outputting images, I find that maybe 1 in 4 images has a black box overlay on it in some random location. Anyone come across this?
Try using pvbatch in batch mode? Pvpython is generally used interactively. Also, be sure to read the header from your trace. It tells you how to edit the trace for pvbatch.
Pvbatch, and pvpython are described in the ParaView Guide. You can find this through the Help menu. See chapter 1.3 and 1.5, and especially all of chapter 14.9 (for pvbatch).
Alan