It should just divide the amount by the limit price and submit a guaranteed limit order for that many shares rounded down. It shouldn't try to do some just in time cancellation nonsense or prevent you from doing short sales using a quantity by amount order preset. The 'cash estimate quantity factor' field shouldn't exist because it's only relevant to market orders that no one should ever use.
Because of this bad design I have to create a different quantity order preset manually for each ticker and can't just have it fill that automatically by dividing $10k by the price.
Simply change to another broker/trading platform. There are hundreds of them for you to choose from. It is not wise to get angry over quantity by amount 'problem'.