Impossible to add a subsequent mention after inserting a new line with `Shift + Enter`

[mabryl]

📝 Provide detailed reproduction steps (if any)

1. Add a mention in the editor by pressing @ and choosing a user from the list
2. Insert a new line with Shift + Enter
3. Try to add a subsequent mention in the newly created line by pressing @

✔️ Expected result

The list of users who can be mentioned should expand and allow you to choose a user to mention.

❌ Actual result

The list doesn't expand, a new mention cannot be inserted:

https://github.com/ckeditor/ckeditor5/assets/72079603/07627e78-e0af-40b1-a908-fc79559a421c

📃 Other details

The issue doesn't appear when you first create a new line with Shift + Enter and then add a mention. It only occurs when a mention has already been inserted in the first line.

• Browser: cross-browser
• OS: cross-OS
• First affected CKEditor version: N/A
• Installed CKEditor plugins: N/A

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If you'd like to see this fixed sooner, add a 👍 reaction to this post.

[andrew-y0u]

We have the same problem. CKEditor v40.0.1

[guillome2k]

Copy that. Hope it will be fixed :)