Didn't see anything like this in the forum history. Converted 11 to 12 multiple times as test. Got no error messages.
Now, value list in that drops in originating file will not longer drop in a second file using the "Use value list from another file". Drop lists in second file on same field do work if using entered values. I have many, many drop list setups like this throughout the muliple files. Tried calling Filemaker support line, won't offer help on this. Outside their preview.