There are a few bugs related to trading cards. I haven't paid close enough attention to determine whether these bugs are native player related or board related, but here is what I noticed:
- Sometimes after trading cards the placement count is not shown any more - refresh required
- in simulgear, when you trade cards commit your orders and then go back to change your orders the cards are untraded again but the placement is made, resulting in a negative placement count. (http://d.pr/i/AOks) Undoing your placements really messes things up.