Automator is an innocent victim here, and it has nothing to do with Mac updates. What you have described is what happens when the Mac Quick Look
feature finds a file that it knows nothing about, typically either when the file has no "dot" extension after the name, or when the extension is unknown to macOS. In that case macOS will attempt to guess what kind of file it is based on the content. A design file with no extension on the name might look like something that Automator can open.
It's not difficult to fix this by following these steps:
- Make sure the design file has a proper extension, such as JEF, DST, etc. If it does not, you can add it by right clicking and choosing Get Info. That will also show you what program macOS thinks should be used to open the file.
- Make sure you have a program installed to open the design. I highly recommend StitchBuddy for this on Macs. Not only will it show the design as an icon and with Quick Look, it can also manage the process of getting it into a USB drive for you.
- If the problem persists after the above steps, it means that the association for opening files of that type has somehow been changed to Automator. That's easy to do with a couple of errant clicks in the heat of the moment. To fix that, right click on the design and choose Open with. If the correct program is not shown in the pop-up menu, scroll to the very bottom of the list and choose other. That will let you choose the correct program. Check the box labeled Always use this program to open files of this type and it will remember.