Rebirth

I did a rebirth on Red Witch and the BR showed an increase initially. But when I brought up the character screen again, the BR is shown as was before.

Then I did a rebirth on Astromancer, and the same thing happened.

In the guides it says that the stats would be greatly improved after rebirth, but in my case the BR has stayed the same.

It seems that I have wasted a lot of timeskip scrolls for nothing.

Is this supposed to happen.

Also, can someone please tell me if you can rebirth a hero more than once if it was working.

Many thanks.