I've never encountered such a "bug", so I dont know for certain - it could be one, it could be something like "okay, second to late/early" (like: you saw someone casting raise on you, so you hit "accept" before it actually landed and returned instead...). But if you file a bug-report and submit all the required information, they might be able to look into this to figure wether its one, lag or an error on your side.