These attempts are on subs that have been launched and are en route to an outpost. On sub highlight, tapped Gift option and waited (both in-game and with game closed) for the 11 minutes to finish. After waiting the appropriate amount of time, the sub was not a gift and the option to make it a gift was still available.
The issue has been sporadic. The gift option seems to work without flaw if selected on pre-launch or when queued / scheduled. For attempts after launch, sometimes it'll work on the first or second try, other times the issue would appear. At first, I had thought it was due to my weak LTE signal, but I was still having troubles on a good wifi connection while being able to make other actions without issue (scheduling launches, hiring specialists, etc).