You have used “French”. That’s often enough for AI to think you wrote in French.
You can manually set the language before submitting or after detection by using this button in the composer.
Regarding your second issue, I think the problem is that you aren’t looking at the original but the “English translation”. Your first screenshot says the post has been edited since it was translated, and the translation might be outdated (and the orange color of the icon also indicates that).
To me, it seems that the translations have been updated in the meantime. Is that correct? I could enforce an update if it’s still needed. (But I don’t think I have the permission to update the detected locale; if you want French users to be able to get a French translation, you will need to fix that. Currently, they will see the original because AI decided it’s French.)