bug with buying new ships in higher ranks

So for the past few days Iv’e been saving up money and upgrading my synergy level on my rank 11 frigate:engineer (Federation). And when i went to but the Chiron rank 12 harpy it wouldnt let me. I had all the money and synergy level but it wouldn’t let me. It did say that in my rank 10 slot that i needed 2 more ships but i already had the rank 11 ship. Also when I went back and bought the amount of ships i supposedly needed it still wouldn’t work. If you have any answer or think what the problem could be please tell me. (all answers will be appreciated.)

It’s an awful levelling wall mechanic that needs to be removed is all. It will continue to annoy you until you are rank 15 in every faction.

Please, attach screenshot woth your ship tree