I had a similar issue. For anyone else who runs into this again to update for 4.27. What helped me finally was doing all the techniques/tips mentioned above.
Plus, making a copy of your project, delete the contents of the content folder, but not the folder itself. Use the migrate tool to just migrate over ONLY the assets from your levels or level, manually move over the player controller, audio presets, video files, the few small things/presets that won’t get picked up by the migrate tool, if there are any forgotten. Copy and migrate is the fastest way to start fresh without creating new project just keep config and content folder delete all the other ones. Unless you want the autosaves, move those to the desktop for the time being, and until you resolve the current packaging issue at least. Then from there your working with just what your using in editor currently, the last thingI had to do was an asset relocalization of every asset in the project, do steps 1-5 from Alekann01’s post above and whalla that worked for me in 4.27. I finally was able to run a successful package.