Time: 18:40 GMT
Frequency: Without fail
World name: Cactuar
Character name: Sylviana Clawbriar
Class/Level: 60 MCH

Steps:
1. One player begins an action with a cast time, such as Hot Shot under the influence of Gauss Barrel. This also includes non-combat actions such as Return or Teleport.
2. A second player requests a trade with the first.
3. The cast is broken and a trade request is sent immediately.

A note that this action can and has been used to harass players, and has resulted in suspensions in the past.

The first thread was moved to 'Not a Bug Report', but to be blunt, if being able to open a trade and thus cancel any casted action is not a bug, what is it? That doesn't seem like intended behaviour at all. Also being able to set "/busy" does not change the fact that the action is possible in the first place, and as something that is used to harass other players & break their gameplay, should not be a work around on the end user's part.