[UE 4.12.4] Light leakage behind certain objects

I am experiencing a strange behaviour in an archive project.
Basically, sometimes, the back of certain objects gets unnaturally bright (as if it was emitting light, sometimes coloured). This seems to be physically wrong, any idea how to get rid of the problem?

The result is similar boh in production and high quality lighting and changing the number of bounces (currently 50)

For example, the back of this couch is glowing:

without the pillows:

without the back:

from behind:

Any feedback?