Render targets for painting - only works in certain maps?

I’ve followed three tutorials to make render targets to paint on ( Unreal Engine 4: Real-Time Render Target Painting Tutorial, Unreal Engine 4 Tutorial - Making a Usable Whiteboard and )

And none of them actually write to the texture, despite checking everything I can, like the coordinates are being properly passed into the texture etc.

I downloaded this VR setup VR Content Examples and it works in my project, but only in the map it’s already set up in - it doesn’t write when the whiteboard and marker are placed in another map. Placing a new whiteboard and marker in the existing map does work, so it has to be a level setting I’ve missed - any ideas? The example content doesn’t have anything relevant in the level blueprint, either.