Unsupported illumination model?

Hi could you tell me what this means, I tracked a plane so i could remove it from the sky, it removed fine all of the way but towards the end as it nears the sun coming through the clouds the remove was obvious, so I tried the different blends-interpolate options to help it blend but got this msg & now can’t remove the last few frames?

Okay, that’s one i’ve not seen before! Can you check you’ve not accidentally set animation keys on the Illumination parameters between the problem area and another point in time? You can check this by selecting the box around the illumination parameters or going to the dopesheet.
Apart from that, i’ll need to check this with the dev team because this appears to be a bug.

It would be great if you could send me this project as it is so we can replicate it.

I can confirm @Gid.Joiner that we will need the project file to see how this can happen. The dev team can’t see why that error should turn up at all so replicating it locally is the next step.

Thankyou, Sorry for the late reply, I didn’t/don’t have the project file, & i haven’t been able to reproduce it, if it turns up again i’ll try keep everything & let you know,
It could well have been me messing Mocha’s head up clicking, undoing & trying different things.
I think i was more curious about what the msg actually meant,
Thanks again.,