PSA from Nimblebit on trading
“There is a gifting bug that occurs when a user adds a new friend when sending gifts. It causes the recipient to get an error message stating they have been sent a gift for a plane not available in their version and they will get 0-2 coins instead. The sender gets a confirmation message when sending but the part and the bux never actually leave their account. We apologize for the confusion this has caused.
It has been in the app for a while but we've just recently figured it out. The programer is working on getting a fix out.
In the meantime, when you send gifts to new friends, be sure to add the other player to your friend's screen before even tapping on the gift button on the parts screen. If they are already your friend, you can gift as usual.”