I have this bug too but my tactical officer is now the same rank as me not higher. I did look and see if I could promote her again and the only reason the game said I couldn't was because I didn't have enough merits not because I wasn't high enough rank.
I tried with my other officers, science and engineering, and the game told me that I wasn't high enough rank to promote them so to me it appears that it's tactical officers but I might be wrong.
Interesting bug/exploit and I haven't searched the forums but I'd be interested in knowing how many people report exploits as apposed to to other bugs that hinder their game instead of enhance it.
Also have BO's with multiple skills in space @ ensign level. This happens when you replace a skill @ skilltrainer with the skill window open when there is some latency/lag. Then it doesn't actually replace the skill but add the new one and then remove the old one (the latter won't happen).
If you don't reopen the skill window you can put skillpoints in both the single BO's multiple space ensign skills.
they do count to BO skill points given in order to promote him, but you cannot access the second skill in space combat in any way. (so consider them lost)