I'm having trouble creating more than 2-3 islands. I've also confirmed this issue is happening on the version packaged with FTB Infinity Evolved Skyblock and the latest version posted on curse.

In FTB, I type /island create and no problem. Makes an island. I do it again. Again makes an island. I do it again. It says I made a new island, but teleporting to that new island it turned out to be Island 1 instead of Island 3. It's overwriting the islands. I tried it multiple times to confirm it keeps happening. So right now, I can't make more than 2-3 unique islands. One time I got it to make 3 islands, but then the 4th was actually the 1st again.

Also, is there a way to manually specify where a new island will be generated? We wanted to make the islands close to each other to build bridges between them.

Because its taking your username by default if you don't give it a name. Meaning you are using the same name every single time. This is not a bug, this is user error