I've been running into this problem with all ShaderToy (GLES/WebGL) nodes, where it works fine when initially plugged into a graph, but then on reload of a project, it renders black (or maybe not rendering at all, I suppose). There are no errors given.
However, when I delete that node and replace it with another one of the same type, it works again. Save it and reload it, and the same blackness occurs. Are there any workarounds to this?