Days when significant non-field-aligned diffusion of cosmic ray diurnal anisotropy occurred during 1965--1968 are studied in detail. It is shown that whereas a large hour-to-hour and/or day-to-day variability of the interplanetary ecliptic magnetic field direction may favor non-field-aligned diffusion, it is not a necessary condition. Some characteristics of the diurnal anisotropy seem to indicate the possibility of more than one mechanism (sources and/or sinks) operating simultaneously, distorting the usually assumed simple picture of a radially outward convection and a field-aligned inward diffusion giving the observed vector along about 1800 LT in space.