Lighting affected by transparent object placed in the map causing blackening

For some reason I have yet ot understand, when I place a transparent object in the map threre seems to be ‘blackening’ or a loss of light until the object is destroyed or hidden.

Without transparent object (above). Nice lighting.

With transparent object. Everything gets darker and the glow effect has reduced. It is almost like the transparent object has sucked the light in.

(Note the door is just placed for experimental use…

The emissive input of the semi transparent material I have tried as zero and not being set at all the result is the same.

Any ideas of what could be wrong?

Can you show me your material editor, please?

Actually it looks like an issue with shows. If I disable shadows for the object the problem goes away. Perhaps physics for shadow might help?