From where are you packaging the game? unreal editor? visual studio? or UnrealFrontEnd.exe?
Try packaging with unreal front end, and try with some different configurantions (shipping, development, cooked, on the fly) and see if some configurations works for you.
Also use the “fix up redirections in folder” on the editor (right click on content folder, inside the content browser).
Some months ago I had a similar issue caused by some different “corrupted” assets over the project (from blueprints until textures)