This is a "not sure if it will work" answer, but the degrees of freedom look a bit wonky, and it is probably because you are using the Kenward-Roger denominator degrees of freedom with a very sparse dataset due to the missing values. Try, in order, ddfm=satterthwaite, ddfm=bw, or using ddf= with fixed values based on a skeleton ANOVA table. You could then add in an EMPIRICAL option to get the shrinkage estimates.   SteveDenham ... View more