Cursor keeps rewriting my whole form component instead of fixing the bug

The bug is almost certainly two submit paths: a <button type="submit"> inside a <form onSubmit> and an onKeyDown handler that calls submit on Enter. Enter triggers both.

Remove the key handler, the form already submits on Enter:

<form onSubmit={handleSubmit}>
  <input name="email" />
  <button type="submit">Save</button>
</form>

For the Cursor loop: select only the onKeyDown lines and ask "why does this fire together with onSubmit?" A question about cause gets a smaller answer than "fix this".