Hi there,
In my project, there is a ExportMask node that isn't exporting its texture mask.
Overview
There are two import nodes, one importing the raw heightmap, and another importing a "freeze" mask, because there are places where the game designer wants to keep unchanged.
At the far right side, there are four export nodes.
After invoking ExportAll from the C# API, all maps should be exported, but the grass mask doesn't get exported. If I select File > ExportAll..., it works without errors.