Hey funk thanks for such a detailed reply.

I actually got it working 2 hours after submitting this post, but couldn't take it back as it was already out pending approval from the forum moderators and was out of my hands.

It was exactly as you wrote to the letter. It was all because of toon lights ...

I assign IDs to my lamps, in Render Settings I click on the pass numbers to enable them. So here's the weird thing: clicking on [1] makes all my lamps appear. Clicking on [2] makes none of them appear, despite some of them having an ID of '2'. If I don't enable light IDs action, clicking on [1 ...