Multiple Image inputs in Blendmode Shader

Question

I'm using 3 input images in a kernel destined to be used as a Blendmode.Shader. As the documentation states, I have the background image as the first input, the foreground image (to whose bitmap I apply the Blendmode) as the second input, and a third image which is to be used to transform the output colours. The third image is passed to the shader by actionscript as per the documentation.
The shader works as it should in the PB Toolkit, and also if I use it in a Shaderjob, but if I use it as a Blendmode it breaks down and the third input image seems to be the problem.
Strangley, if I strip the shader of all code and leave only:
     dst = sampleNearest(ThirdInputImage, outCoord());
the output gets filled with a single colour and not the third image's pixels as would be expected.
Are there any known issues with using three or more input images that I may have overlooked?

Answer 1

It's likely that you unknowingly hit the "F4" key, and swapped the "Switches" panel, for the "Modes" panel.
Try hitting F4 again to toggle back to the switches panel.
If that doesn't work, right-click on the panel title bar area:
And, in the Columns fly-out, make sure Switches is checked on: