David, you can always edit your own translation. Click on 'edit translation' and make changes. Then click on 'Update'. The original translation is replaced with the edited translation. You can do this as longs as no other activity has occurred in the translation unit, like: someone has submitted a new translation after yours, someone has given an upvote, or someone has made a comment in the Discussion box. You can only edit your own translations, not someone else's.