I think Reiner's transformation ended up like that because he wasn't particularly motivated.
Like how Eren had a couple of screwed up transformations or that really messed up one in the well when we he was overly tired.
I got lucky and was up the night they went up after the show where they announced the price. It took me forever to get a PS3 so this time I was like, something tells me they're going to go up unexpectedly this time.
So I sat around and got lucky.
Didn't we get a whole filler arc right at the moment we finally reached Aizen? I'm pretty sure I remember that we had to wait to see how they'd take him down.