The sorting of person directories has changed in Omega 5.690. If you have previously entered people using Omega Classic or are opening files created with Omega Classic in versions prior to Omega 5.690, you must at least regenerate the directory of all people and, if necessary, also clear the directories of selected people and recently viewed people . Otherwise, Omega Classic may crash.
Otherwise, you should also check the file.
These measures should ensure that in virtually all cases you can then work with the file again without any problems in Omega Classic.