Here is the pic....

This happens because CC3+ can't render the entire image in one go, it has to divide it into segments. Unfortunately, lighting effects with an origin outside the current segment won't be rendered properly.

You can change the number of pixels used by CC3+ by following the instructions in Sue's post here

Any chance of uploading the FCW to see if we have the same problem?

It's not actually, it only looked that way, causing me to come to the wrong conclusion. Try this version:

It was was an issue of too sharp angled in relation to the width of the line. I misinterpreted it as the light rendering issue, because I was not aware that these stray lines would also block light, the result looked very similar to that issue.
All I did with our drawing was use the REDN (Reduce nodes) command on the wall. You'll notice that it has less nodes than in your original version. This isn't a universal fix for this problem, sometimes you need to hunt down the roughe nodes and remove them individually, but in this case, REDN seems to have done the job just fine (unless you mind the reduced node count)

Posted By: HadrianVIBut you replied at the same time saying something completely different.

Never assume I am always right.