I recently upgraded to Mac OS Catalina (Version 10.15). In Photos (Version 5.0 (101.15.190) ) I keep my albums ordered by date, and I typically export using Sequential to keep the proper order in the exported files (I have photos from different iPhones and cameras, so different file names). It has always worked. Since the upgrade, the exported pictures have a totally RANDOM order, neither by date (as it was supposed to be), nor by location or filename or tag or anything, absolutely random. I tried to use a different sorting option for my album, but the exported photos still have random ordering instead of the proper sequential order reflecting the sorting option of my album.