If you can spell words correctly in practice but misspell them in real writing, the spelling may not yet be automatic enough to survive divided attention. In a spelling exercise, the word itself is the task. In composition, attention is also managing ideas, grammar, sentence structure, punctuation, and what comes next.
Move practice closer to real use. Retrieve the word inside a sentence, use it in short timed writing, compare commonly confused forms, and keep a personal error list drawn from your own compositions rather than from generic spelling lists alone. The goal is to make correct spelling available while the mind is busy doing something else.
Use the English Learning Hub for writing and language routes, and the Vocabulary Learning Hub when word form and retrieval are part of the problem.