Cat suddenly pooing outside of tray

[EvenFlo2]

Help! My 9 year old cat has started pooing outside of her box; so far in different places around the house. She seems well and is using the tray for wee but not poo.
I have changed litter but that was ages ago and she was fine until recently.
No changes at home, no stressors, she seems her absolute normal self, she can get to the box no probs so it’s not that.

Any thoughts? I’m reluctant to take this to the vets as she seems totally well :-(

Oh and the poo is totally normal consistency so not like she has the runs or anything

She doesn't like the litter, she's scared another cat will attack her in there (if it's a covered tray and if you've got another cat!) She is finding pooping painful and associated that pain with the tray??
Personally I would change the litter back and see if she starts using her tray again first. Also, have you moved the location of the tray?

I have moved the location but the problem predates the move (only moved it yesterday). We do have another cat but house poo-we is definitely the boss in that relationship!
Think I will try and change the litter back though - just weird that she never had problems with it before...