Hi @Chris Stephens ，
Displaying read-only requires an extra click, probably because the file is in protected view. Exiting "protected view" can simply enable editing in the message bar, which is normal/expected behavior.
Per my test, using online co-editing should not fail to save, because the files edited in the browser are automatically saved by the system. According to your description, external users may edit shared files through ‘open in app’, which may cause upload failure due to multiple editing. I tried it and got a notification that the upload failed in the image below, which may be ignored by the user. So I recommend ‘open in browser’ to edit shared files with multiple people, which will reduce the failure of saving due to uploading.
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