opening form

Hi Experts,
I have a Access DB in 2007 version (32bit) and I convert to 2016 access(64bit).  I have a login page, user enter the user name and password, then open a form with few buttons (one of these button is open an entry form name "Add/update Case"), this button was working fine in the old version, however, after I converted to 2016 version, when I click this button to open the form,  once the "add/update case" form opens, it circling for about three to four seconds, it close the whole database then make a backup of it.  I checked all the coding and nothing get change.  I can figure it out why.  any help will be very appreciate.

Thanks