Please help, litter box troubles

My kitten is 5 months old. She goes in the litter box about 80% of the time, but sometimes she will have a wee or a poo on the carpet next to the box outside of where the litter mat is. I have 3 litter boxes, 2XL ones and one smaller one. They’re separated on opposite sides of the room in each corner. She has wee’d in the scooper holder a few times and this morning on a new mat that was used under neath her food bowl I’ve put down as a deterrent. She seems to like to do it in corners/ against walls. Shes spot on with it most of the time. I keep adjusting things and trying new things out and nothing seems to have worked. I have tried

A feliway plug in

Adding more boxes in different locations

Changing the litter

Keeping it immaculately clean

Blocking off areas that are problem spots

She always seems to find a new area that I didn’t think of to do it in. She’s so good most of the time but sometimes I wake up and she’s left me a surprise on the carpet

For context I have two, they’re from the same litter a boy and a girl. I got them at the beginning of the year and this has seemed to be a consistent habit that happens once a week but sometimes more. Sometimes I’ll go a week and think she’s getting better and she’ll leave me a lovely surprise in the morning to show me she’s not lol. They are both put in their bedroom over night. At first I was worried the boy was making her nervous but I got a camera in there and i don’t think that’s the case.

I have a litter genie bin behind the boxes, sometimes if I move the box the clean behind there she runs and instantly squats to attempt to wee on the exposed bit of carpet. I don’t understand her logic lol. Any help or anyone who’s been through anything like this. I don’t wanna have to just accept that this is just how she is.

She doesn’t do it anywhere else apart from around her boxes so I know she knows that’s the toilet zone. I just don’t know how to unblur the lines and make it more black and white for her.

Anyone who’s experienced this and has any solutions as all I can find online is older cats doing it or doing it 100% of the time and not just occasionally. Thank you