It's still doing it. I have no idea why, in some places, the scenic glue is drying white. I have used thinned Elmers, Elmer's school glue, Mod Podge, and this time Future (well, Pledge Floor Care Finish) which is clear to start with.
It doesn't do this anywhere else that I'm trying this except my layout.
It's driving me crazy, because the areas where it doesn't happen look great.