I think the ispgfh1 entry in the sph header is actually the number of SPH particles (or around that), and therefor this check throws an error when it shouldn't.
I don't quite know how to interpret the LS-DYNA binary manual for this portion of the d3plot file, however!
https://github.com/open-lasso-python/lasso-python/blob/2efed713789285ab5840fe6c5c50f0a72c8eeb3b/lasso/dyna/d3plot.py#L2232
I think the ispgfh1 entry in the sph header is actually the number of SPH particles (or around that), and therefor this check throws an error when it shouldn't.
I don't quite know how to interpret the LS-DYNA binary manual for this portion of the d3plot file, however!