For some years, I worked in localisation and UX writing for apps and websites. Most of these jobs involved just a few strings of text from time to time. They were usually small jobs for digital products that were already in the market. Localising this kind of products usually involves UX Writing because it's not just about language and tone, you have to be very careful with other details, such as the user journey and the limitations of space, specially in the case of mobile apps.
The most prevailing problem when you work with products that were initially translated by another person is that in many cases you don't have a translation memory because the client doesn't have those files. That meant that I had to check the product constantly to see if every sentence or term was already in use. In UX Writing is important to be consistent. Even if the job consists only of a few strings, it involves several layers of complexity and many hours of work.
Languages: English > Spanish.