surfaces randomly emitting light

[NvDartel]

As described in the title, lately I've had some renders in twilight render where surfaces randomly emitted light. as an example I added some pictures of a row cardboard boxes on pallets. they're all exactly the same and put apart at exactly the same distances (they're duplicates) yet when I render this sketch some surfaces start emitting light for some reason, what makes it more weird is that these surfaces are not consistent with different viewing angles. I'm pretty new to rendering so could someone help me out on this?

Thanks,

[Fletch]

This is from low quality photon map.
Use higher quality render setting.
For this scene, Easy 08 would be a good choice for final quality.
Low quality render settings are for test phase.

[NvDartel]

Thanks for your comment, I'll try out some new renders with higher settings on the same model and see how it turns out. will report back here with results