I see this from time to time and it is nerve wracking. Here is one thing I have found that sometimes solves the problem.
Look or search recursively in the project directory for any *.log file. Look in that file with Wordpad so that it doesn’t look like a hash of text like Notepad would show. Scroll down to the bottom and look for an error message about an orphaned file, usually a menu. In the project edit that menu in Photoshop simply saving it as a Photoshop file to some different name outside of the project. In Encore delete that menu. Quit Encore saving your work. Restart Encore and add that Photoshop file as a menu from the external location. Reattach whatever it had and run with it.
More than likely if there was an orphaned file this will fix the problem.