Preconditions:

• Clean installation of Content / Experience / Commerce
• Installed language e.g German (composer require ezplatform-i18n/ezplatform-i18n-de_DE)

• Tested on changes from PRs: 
  https://github.com/ibexa/admin-ui/pull/377
  https://github.com/ibexa/content-tree/pull/32

Steps to reproduce:

1. Log in to back office.
2. Add new German language in Admin / Languages.
3. Go to Content / Content structure and expand Content tree.
4. Select "Ibexa Platform" content in content tree.
5. Click on option button for "Ibexa Platform" content in content tree and create new content Folder.
6. Add new translation for created Folder content through content tree.
7. Create a new Article under Folder content through content tree.

Actual result:

See attached screenshots and watch gif please: https://recordit.co/sVzUsduoJ8

Cannot create a new Article content when parent folder has added translation.
An error 404 not found occurred.

Could not find 'Content' with identifier 'array (
'id' => 134,
'languages' =>
array (
0 => 'eng-GB',
),
'versionNo' => 1,
)'

Expected result:

User can create a new content Article through content tree with different translation than defalut one.

Update:
The issue is not combined with mentioned PR's. Problem also exist on mentioned branches in affect version section.