When I lived at my Mum's we had two cats who spent the day outside and had a litter tray each inside. I noticed a couple of things -

Firstly, if the litter tray got "full" they immediately went elsewhere.

Secondly, no matter what the state of the litter tray was, if there was newspaper or plastic nearby they would urinate on it.

Thirdly, my younger kitty, Whiskey, used to use urination and even defecation as an act of defiance! Deny her food outside normal feeding times, keep her inside at night, move 1000 k's away - it was all a great excuse to use the shower as a bathroom! After I moved interstate, her problem became serious and she was doing it every day. Then, as time went on, she would do it less and less. My Mum solved that problem by being patient and keeping the bathroom door closed at all times!

My point is, often it is a mixture of behavioural issues (such as you present emotional situation and moving) and pragmatic issues (having a wonderful couch to pee on!) ... all you can do is continue your undying patience and try whatever you can!

All I can say is I'm glad your kitty has a wonderful and loving Mum who is willing to be patient and loving!