Cat pooped outside of box while we were away

Hello!

I guess I am just looking for a second opinion.

My partner and I had to travel to visit family over the holidays so I booked a pet sitter to visit twice a day to visit my 2 cats. The first night, the pet sitter reported a small present in the office part of our home. I didn't think it was a big deal - sometimes they eat my hair and have a "chaser". We had left at 3pm and she visited at 8pm. She cleaned it up and the rest of the visits were fine; it was a 2 night trip and they visited the morning of our return as well.

About a week later, we had to stay away for one night. I fed them their evening meal as normal, plus some extra, we selpt elsewhere and came back in the morning.

This time there was a small pile of poo in front of our patio door.

One of my cats (male, 6 years) is definitely not the culprit. My other cat (male, 4 years) is most definitely responsible.

I'm going to get a pet camera for future, but this is incredibly abnormal for either of my cats. They have always both been extremely clean. Now that we are back to regular non-holiday schedule and home every night, there's been nothing.

Both are well hydrated with multiple water sources and wet food. No changes to diet. Both my cats are incredibly affectionationate sweetie pies and spend quite a lot of time with me.

If it happens again I'm going to bring them both to the vet, but is it likely this is a health issue or just being upset that we left?