IMHO not a FileMaker Issue, seems to be a problem with the design, maybe the DB-file
Try to add a refresh window (either add a script step if there is a script for browsing records - or create a script for testing purpose that goes to the next customer and refreshes the window) - with flushing caches
Are You running FileMaker on a local machine or are You connecting to a server?
Please note that you have provided no real detail as to how your database and this layout is designed. If you described that, we might be able to identify the problem keeping this from working.
Please also note: Report An Issue is intended for Reporting Possible Software bugs. Questions on how to work with FileMaker Pro should be posted in the FM Pro Forum Section. (See tab at top of this screen.)