'Copy value from site...' doesn't save properly

[tommysvr]

Description

When copying a value from another site, the changes don't persist on save.

Steps to reproduce

1. In a multisite setup with fields set to translatable, add differing content to Site A & Site B
2. On one site, click ... -> Copy value from site...
3. Save the entry

CleanShot.2026-05-13.at.11.58.35.mp4

Expected behaviour

Content is saved properly

Actual behaviour

Field is not marked as dirty & changes are reverted

Additional info

Reverting to CkEditor 5.3.1 resolves the issue. Looks to be related to this change in 5.4.0: #555

• Craft version: 5.9.23
• PHP version: 8.4
• Plugins & versions: CkEditor 5.4.0 / 5.5.0

[linear-code]

PT-3119

[jbalmer]

Thanks Tommy 🙏