Re-litter box train my cat

One of my cats will pee, but no longer will poop in litterbox. Took her to the vet, no medical issues.

I adopted 2 adult cats about a year ago and am a first time cat owner. The cats previously used clay litter, and were slowly transitioned to tofu litter over the span of a month without issue and had no accidents.

My female cat first pooped right outside the litterbox when I left for a weekend. After a couple days, she started using the litter box again to poop. The next month I traveled, when I came back the same behavior happened. She will poop outside the litterbox for a few days, then go back to using the litterbox fully. I travel about once a month, and have noticed this pattern every single time. My cats are always watched by people they know when I travel, and their litterbox is always cleaned daily.

I thought it was due to anxiety, but when I traveled most recently, my cat completely stopped using the litterbox to poop. It has been about a month of her pooping outside the litterbox, she will still use litterbox to pee.

I tried getting a 2nd litterbox with same tofu litter, didn't work. I have tried using litter attractant and litterboxes are cleaned daily.

My cats are both spayed/neutered, up to date on shots, no medical issues, and get along with each other.

Any tips on how to re train my cat to use litterbox for all bathroom needs/litter type advice?