Our cat keeps shitting in dds room 
He has a litter tray (downstairs) but that seems to not be being used at the moment so guess he does most of his business outside.
He was going through a habit of pooing in dds room once a fortnight maybe but I thought he had stopped it as not happened for a while.
Last night he did it again and I was so angry, dd picked it up and thankfully we stopped her before she put it anywhere else like her mouth. He's then done it again this morning!!!! 
I'm assuming it's because he can still smell it no matter how well I clean it and so now thinks of it as his litter tray. Thankfully we are moving house at the end of the month so no shit scent for him to follow, but how can I make sure he doesn't start again in the new house?
I'm so upset and angry, I love him and would never get rid of him but this has to stop.