Random urination on carpet

[Garysmum]

My cat has lived with me in the same house fully litter trained for 10 months.
I used to go away for the odd night and all was well. I went away for 5 nights in May with a neighbour going in twice a day- no problem. In July though / 5 night same neighbour she started urinating on one patch of carpet but used litter box for poo.
since then if I go away for a night sometimes she has done the same thing. And this week I left her one evening for an hour - it happened again.
I cleaned the carpet with enzyme cleaner.
It’s been 3 weeks perhaps 4 since the last one. There have always been lengthy gaps.
she does prefer going outside but I have made no change to her litter box which has used same litter all time. No cat flap (can’t install one for complicated reasons).
I am wondering if I should take her to vet -4 weeks in 4 months isn’t a lot but it’s odd.
i could also restrict access to the pee patch.

any other thoughts - no changes to home otherwise, no new pets, humans, new neighbours but they have no pets.

Could she be scared of something outside like a Tom or something and when you’re not there she’s not brave enough to go near her tray?

You could try putting another tray in the pee area she could use if she’s scared. Keep the existing one where it is.

Really good point. Litter tray is near back door and she is going upstairs. There are 2 large male cats near by that hunt at night and come into the garden.
I will dig out another tray and give that a go,

When our cat started weeing in one spot I had no choice but to put another tray on that spot. Once the idea is in their head, unfortunately it tends to stay there.

Perhaps the neighbour isn't as good at cleaning the tray as you are (or twice a day isn't enough) or as others have said, perhaps something has spooked her when you're not around.

Is she locked in when you are out/away and would generally wee outside?

Ideally she should have two litter trays anyway so definitely a good idea to put one where she's having accidents.

There's been a few cases like this on the show "My Cat From Hell" and the consensus is generally that the cats are scared of something outside and don't want to pee out in the open as it leaves them feeling vulnerable.