Thank you for your post.
I'm unable to replicate the problem, and I know that doesn't help you. If you create a new layout (do not duplicate) with the same fields, does it also occur? Does it only happen wihin a tab control?
Regardless, I would like to get a copy of your file (no records necessary) so I can determine why it is not working. Check your Inbox at the top of this page for instructions where to send the file.
Try adjusting the size of the object just a bit.
I connect my IOS devices to the Filemaker Pro 12 computer via wifi and open the file on the ios device so that I can verify the layouts as I work.
Mostly the layouts of the IOS devices will update when I return to browse mode from layout mode but sometimes they do not and I have to quite Go and reopen the file for the update, not that often.
I create separate layouts rather than trying to get one layout to work everywhere since the screen dynamics vary from Mac to Windows to IOS and having FORM tablename iPhone and FORM tablename iPad and FORM tablename Mac and FORM tablename windows and even Form tablename IWP can save a lot of headaches.
Using a separate layout fo the iPhone vs iPad forces me to think a bit differently and reduce my expectations and output...