you could check the following:
6^: l
?0;b}Xl-
- if the surface/element tilt is too large !P92e1
u%[*;@;9+
- enough analysis rays used? $~~=SOd0
\K?./*
- have you used Coherent Data option under Detector setting. {Ue6DK%
G(0bulq
Someone above was right about that the non-sequential mode only uses geometric rays but you could see inteference fringes using Coherent Data.