The MoveV2Async method is the right way to move an existing file or folder, so it looks like you already have the right idea. It sounds like you're getting the 'too_many_write_operations' error though.
The 'too_many_write_operations' error indicates "lock contention". That's result of how Dropbox works on the backend. This is a technical inability to make a modification in the account or shared folder at the time of the API call. This error indicates that there was simultaneous activity in the account or shared folder preventing your app from making the state-modifying call (e.g., adding, editing, moving, or deleting files/folders) it is attempting. The simultaneous activity could be coming from your app itself, or elsewhere, e.g., from the user's desktop client. It can come from the same user, or another member of a shared folder. You can find more information about lock contention here:
https://www.dropbox.com/developers/reference/data-ingress-guide
In short, to avoid this error, you should avoid making multiple concurrent state modifications. E.g., don't issue multiple such requests at a time, and use batch endpoints whenever possible. That won't guarantee that you won't run in to this error though, as contention can still come from other sources, so you may also want to implement automatic retries in your app.
