Forms fillable fields / Alternate Layout

I created a generic form (using a "custom" page size - 8.27x11) and included the Interactive fillable fields.  When I exported to PDF and tested the fillable form, all the fields worked and were in the order I placed /arranged them using "Tab Order".

I then choose "Alternate Layout" - specifically A4, exported to PDF again, but his time some of my fields became out of order.  I went back and cheked my "custom" form (just to be sure) and it is ok.

Any help on this?

Thank you!