usually these kinds of slips (called expressive errors or paraphasias in writing/typing) happen when the brain is translating thoughts into language faster than the fingers can keep up, annd relying heavily on muscle memory and autopilot. When typing quickly without full attention, the mind races ahead, leading to omitted words, wrong similar-sounding words, or incomplete ones. A lot of people ask me about this, and happens moreso during acute stress or anxious periods....like when you really want winter to arrive after three years and it still hasn't.