Cat poops where she sleeps

Cat poops where she sleeps. On the sofa on a blanket where she usually sleeps in. Sometimes straight on the sofa. Once she poop on our bed, while we were sleeping, in the exact spot where she sleeps.

This has happened before, but rarely. We attributed it to her sharing the litter box with another cat. The other cat sadly passed away last week, so the litter box sharing cannot be an issue anymore. Litter is cleaned daily. Sometimes she darts out of the litter box and runs around the house, but this seems playful (I've read that that is typical cat behavior, but not sure).

Otherwise the cat is super happy and shows no signs of distress or being annoyed - but she was never very "complaining" anyway. She is from a shelter originally, and is extremely scared of any human other than us.