Trouble converting/opening project created in iOS

Windows 7 Enterprise Service Pack 1
Beta 29

What happened:

  1. Created a new project on iPad Scrivener app located in dropbox folder. Added three short files across a few days (containing text only, typed on iPad) to the Research section of the project. Synced the project.
    Opened beta 29 on windows laptop, selected ‘open existing’ and navigated to the new project. Got the prompt about this is an old version, would you like to convert and back up. Selected OK. A backup was created, but the project did not open. Tried this a few times, same result (with an additional backup) each time.
    Tried opening the project by navigating to the scrivx file in Explorer and double clicking; the file opened fine in Scrivener 3 (I also have 1.9 installed), so seems to have been converted properly.

  2. Tried to replicate this by making a new test project on iPad and typing some random text into a couple of notes and saving it to dropbox.
    Opened beta 29 on windows laptop, selected ‘open existing’ and navigated to the new project. It opened fine, no prompts about conversion.

I do not know what is different about the two files except that they contain different character strings.

Is there anything you’d like me to look for? Since they contain so little I would be quite happy to share the files in case there is anything more here than a weird local quirk. Let me know.