Hi MVS, I recently purchased an innokin iSub APEX along with some atomizers and received them Friday 03/24. While preparing the APEX for use, I turned the top cap to reveil the fill holes as I would do with my innokin iSub S. I noticed that it was somewhat more difficult to turn than my iSub S and found that once it was opened, it would not close to seal the fill holes. Can you assist? I would like to exchange this item for one that works properly. Thank you