Tokina rmc 2.8/24 PK, reversed element?

[Aanything]

I bought a RMC Tokina 2.8/24 in pentax K mount. It was super cheap because it had stuck aperture, and having already dismantled some rmc 2.8/28's I was quite confident I could fix it, so I bought it.
Aperture now works like charm, but the lens shows signs of a possibly reversed element - almost complete lack of sharpness except for the very center and blur increasing in the corners, basically.
I was quite carefully in putting things back in the same way they were before I opened it, and I didn't try the lens before opening: so it probably was already like that when it arrived - or maybe I made the mess, it doesn't matter.
Does anyone have a lens diagram of this lens, or something that can help me in identifying the wrong positioned element?
Thanks in advance.