missing density band when using SampledDensityMaps

[ichem001]

When creating high-resolution EM map with SampledDensityMaps, some of the density planes are empty (missing?), creating a stratified effect not present when comparing to maps created with other softwares. I included a screen shot as an example.

code use: /* Start / IMP_NEW(em::SampledDensityMap, dmap, (mod_ps, res, apix)); / End */