What should I do about my cat?

My cat is about 12 years old. Recently she had an impacted anal gland that also became infected. She is fine now, completely healed, but ever since she has started doing her business outside of her box. This has never been a problem in the past. She doesn’t do it all the time, about 3–4 days in a week, but some days she won’t even use her box. I know cleanliness is not the issue, we scoop 2–3 times a day and change the litter 2 times a week. Does anyone have experience with this sort of thing