First, c000ni from Cabin Boy (after relinquishing captaincy) to First Mate in 4 promotions (I have 2 accounts, c00ni and c000ni, don't get confused): HAYLO demoted 4 times from First Mate to Cabin Boy, then back to First Mate in 3 promotions with me remaining Captain:
This bug continues to exist in 2.0.1 The second promotion did nothing and required a third to get to first mate.
Still exists @c00ni. Happens very often! I think the only solution I have found to this is to wait a couple of seconds before each promotion/demotion, and then it works fine. Doing it too many times, too fast, results it in missing the entire command itself I think.
I've noticed in the past that if I do it from the shortcut in guild chat, it has issues, but if I scroll down the guild member list and do it from the guild page itself it takes every time. This could just be because of the increased time between requests, as skillzone suggested. A semi-related issue is if a captain promotes you to captain, and you go to promote them from guild chat before either of you has typed anything else, sometimes it will ask if you want to make them captain again, rather than boosting them from powder monkey to crew. If you hit yes, you go to powder monkey, and they go back to captain.