Bleach: The Plot Hole I Was Talking About (SPOILER ALERT to non-manga readers)

Well my first post is about the transformation of the characters.
One of them is Ichigo, who was forced to go to the Palace to get his zanpakuto fixed.

I thought it was a plot hole. It was said that no one can fix a broken zanpakuto other than Oetsu...

but if we look back on Aizen's betrayal, he destroyed Renji's Zabimaru in its shikai form. Renji then made a special move to use his broken zanpakuto to his advantage. Apparently it's another plot hole. Really? You know a move that requires your zanpakuto broken? So does that mean that Renji broke his zanpakuto before? Or is he breaking his zanpakuto to practice this attack?

One can argue that Renji's bankai can do the same move by purposely disintegrating his zanpakuto. However in the chapter/episode, Aizen visibly destroyed it with Renji totally surprised by the act. Also, we can see remnants of "break scars" on the edge of the pieces of Zabimaru.

After this incident, Zabimaru fixed itself through unknown means.

So yeah, its' a plot hole.