ClayMode

I have a problem with using claymode. When the scene finished render and restoring materials have done, i indeed have almost all materials left assinged as clay material (especially on multi/sub-object and itoo forest / railclone materials). And very few materials in mat.editor left.
P.S. After update to 1.2.4 I see this problem time to time, but i can't figure out in which cases it happens.