4 year old suddenly going outside the tray

[FrostyPopThePenguinLord]

Our 4 year old female house cat has started missing the litter box when peeing. Her (much larger) brother has been having no issues at all.
They are the biggest trays we could find with as high a side as we can find. Enclosed trays they don't like. She has also stopped burying everything, her brother has started going back to bury it.
They have no marking issues around the house, both are neutered and the trays have been in the same place for over a year and we have always used the same litter which suits them well after much trial and error when they were little.
I think we should take her for a vet check up just in case she has a water infection or something.
My husband thinks its behavioural as she doesn't do it every time she pees.

Basically we are out of ideas, if it's behavioural I don't know how to stop it. The trays are on the kitchen floor, we are carpeted everywhere else so we are not moving them.

Any advice gratefully received! I'm pregnant so not keen on strong smells, any smells really, I've got a nose like a bloodhound atm.

I don't know. A UTI wouldn't cause her to piss over the sides of the tray. I think I would have to try to get them used to enclosed trays. If it's very big, with a big front hole and no trap she might not object?

I did think that, but I wasn't sure if she was peeing over the side because she didn't have time to pick a place to squat properly, I know thats how I felt with a UTI once.
Or if not a UTI, a sore back or something, I just wanted to rule anything medical out before we went and bought a bunch of new trays. It's what we do for the horses if their behaviour suddenly changes, we get the vet and saddler to check them.
The problem we have is they are truly massive cats, think mutant ragdolls on steroids, we have the largest open trays we can find, everything enclosed is either much smaller or the door is too small. Neither of them like enclosed spaces much, the vast majority of cat caves etc are far far too small and they have never used them.

Well there is no harm in getting things checked out. With a UTI they normally keep on trying to wee and keep returning again and again to the tray. A check up can't hurt though.

You can always put puppy training pads under/around the trays to mop up any wee that goes over the side.

What about this?

www.petmeds.co.uk/Kokoba-High-Sided-Cat-Litter-Tray/p/I9201296?=googleshopping&_fp1=ppc&_fp2=813892079&_fp3=41654447883&_fp4=I9201365&gclid=Cj0KCQjwq7XMBRCDARIsAKVI5Qb30KdCC98Imb15oiGote5g_sUv9EH0P8EetA7c87N__D2jIeD93s0aAmX_EALw_wcB

https://www.petplanet.co.uk/product.asp?deptid=5933&pfid=62182 this is the tray I have. I needed the high sides as one of mine likes to create mountains with the litter

https://www.petplanet.co.uk/product.asp?deptid=5933&pfid=62182 does this work?

dementedpixie I can't get your link to link to a specific product

It's called Purrshire Anti-bacterial Cat Litter Tray with Scoop - XLarge

A side view. Both mine can fit in at the same time at the moment

If it's behavioural rather than medical, have you got space to stand the litter tray in a washing machine (or similar) drip tray so at least the urine is contained?

I'm going to take her to the vet next week just to be safe but we are looking into bigger/higher sided tray options, thanks for all the ideas guys.

The trays we currently have are more than big enough which is which it's so confusing as our much larger male cat is totally fine with it.

She did it earlier, got in turned around and did a half squat at the very edge of the tray and got it on the floor again. Doesn't seem to have this problem with poops though which makes no sense. If she had issues with aim a poop would me more likely to go on the floor wouldn't it?
We are at a bit of a loss but if she is cleared by the vet then it might just be a matter of switching trays up.