I presume that your system settings also specify the yyyy/mm/dd date format, yes? (That's the one I prefer, as well, and it's the international standard sequence under ISO 8601.) In the problem file, go to FMP's "File" menu, choose "Save a Copy As ..." of type "clone (no records)", and click on "Save".
If the initial file is "XYZ.fmp12", the one you save will be called "XYZ Clone.fmp12". (You will later discard the former and rename the latter back to the original name.) The date formats in the cloned file will be set up to operate the same way as whatever your current system settings are.
With XYZ (original) still open, make sure that you've selected "show all records" in every table within it. Then go into XYZ Clone and, for each table, used File > Import Records > File... > XYZ (with the matching names option as shown below) to specify that you want to import all the records from the corresponding table in XYZ. As part of this process, the dates should all be converted to the yyyy-mm-dd format.
The cause of searching problem can be broken index.
To rebuild index, set storage option of the field index to "none", (close file), then restore setting.
OK thar sounds like a good idea.Going to try that out. Thanks for the help!
First tried the simple solution of 19752 - rebuilding the indexes (with restart). Unfortunately didn't solve it, but thanks for thinking with me.
Then tried Richard's (more work) solution. That 'solved it all. Thanks Richard!
FWIW, importing into a clone also rebuilds all indexes in the file.