When creating a content in another language than the default one, several "Not found" errors can occur.

# Build
git clone git@github.com:ezsystems/ezplatform-ee.git -b v3.0.4 ~/www/ezplatform-tmp;
cd ~/www/ezplatform-tmp;
docker-compose up --build --detach;
cp ~/www/ezplatform-ee-docker/auth.json ./; # Use an auth.json giving access to eZ Platform EE
docker-compose exec app composer install --no-scripts;
docker-compose exec app composer ezplatform-install;
docker-compose exec app composer run auto-scripts; 

• Connect to http://localhost:8080/admin using admin:publish
• Create a language in http://localhost:8080/admin/language/create ; for example Français (France) | fre-FR (let Enabled checked).
• Go back to Content > Content Structure and use Create right panel to create an Article in Français (France)
• The article form open at http://localhost:8080/admin/content/create/nodraft/article/fre-FR/2
• Fill mandatory fields (Title and Intro)
• Click on Publish button
• An error occurs: "Could not find 'Content' with identifier 'array ('id' => 55, 'languages' => array (0 => 'eng-GB', ), 'versionNo' => 1,)'"
• Go to http://localhost:8080/admin/dashboard
• In My content > Drafts tab, this new article appears
• Try to edit it by clicking on its pencil button
• A red "Not Found" notification appears

# Destroy
docker-compose rm -svf;
cd;
rm -rf ~/www/ezplatform-tmp;

This also happen with ezplatform-ee v3.0.3 and master (3.1.0-dev, 6977a84). (For master, you'll need an auth.json allowing access to ezsystems/ezplatform-page-fieldtype; personally, I used my GitHub.com credential.)