I think I've seen this in previous patches, but I just repro'd it on the latest one. If you have a spy that earns a promotion and then move the spy that turn instead of promoting them, they are no longer eligible for a promotion when they get to the new city. The turn my spy earned a promotion, his exp bar was full and said 7/7, whereas after moving back to a friendly city no exp bar was visible and the promotion ability wasn't in the action bar.