I have experienced references to actions getting lost, so I created bug ticket here to keep of the issue.
It last occurred during the following condition:
1. I added an action to a dialogue line.
2. The action appeared as normal when in editor mode.
3. When pressing play, the action was replaced with a missing action.
4. When stopping, the action was still missing.
5. In the log, the following entry was generated: "GameObject (named 'Dialogue') references runtime script in scene file"
The steps 1-5 can be repeated, and each time with the same result.
I'll follow up more info after trying debugging the issue...
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