We've had a slightly similar case in support some time ago, and the solution was to remove an object which has Corona Light mtl applied to it, as it had over 4000 triangles.
It is advised to use as simple light-emitting model as possible (e.g. just a plane, or a Corona Light with shape set to disk, sphere, etc), and a separate geometry for the part of the light which is glowing, but does not cast any light into the scene.
Let's wait for the scene, but my guess is that this will be something similar.