Really weird refraction problem

[increase]

So this is a problem that sometimes pops up in our render pipeline. I think by now I must have tried every trick in the book to get rid of it, but no luck.

Attached is a scene as stripped down and clean as I can possibly get it. Three objects. One has a refractive material, the other two have a default grey material.
I used a fog color because it highlights the error quite nicely, but it happens all the same.
Deleting one of the grey objects fixes it, but it doesn't get me any closer to a solution.

Any ideas?

[tashko.zashev]

Hi,

This result is very odd.
I can get the same issue with your scene, but if i made new one with same materials and models created from scratch, it doesn't appear.
Can you share some details about the objects, are they imported from other application?

[increase]

Hi Tashko and thanks for the answer.

In the end I found out that the glass object was created with a script, using a mirrored x-axis.
Somewhere along the way, any indication of that mirroring had been lost, so the object seemed technically correct (normals, transform...).
That's why the usual tricks like Reset XForm didn't work either. Something must have gotten messed up within the mesh data

The same thing actually happens if you just create a box and then mirror it in some axis, but that's an "expected" result I guess.

[tashko.zashev]

Thank you for the update on this.
If you have a reproducible steps to achieve this result from scratch, i can add it to our bug tracking system.