Failed to grab locks

The "Failed to grab locks for" message indicates a technical inability to make the state modification in the account at the time of the API call. This error generally indicates that there was simultaneous activity in the account preventing your app from making the state-modifying call (e.g., adding, copying, or removing files) it is attempting. The simultaneous activity could be coming from your app itself, or elsewhere, e.g., from the user's desktop client. The best practice when receiving this is to just retry the request, respecting the `Retry-After header if given, or after a small delay possibly with an exponential back-off. If the activity is coming from your own app, you should avoid making multiple state-modifying calls in the same account at the same time.

I don't believe API v2 would improve this, as this is how the Dropbox backend itself works.

Yes indeed my app is submitting for file copy concurrently but there are no way to submit batch copy (folder doesn't fit). If I do sequentially it takes plenty of time to copy files. Let say 40 image files with about 600 kb of size each it takes about 30s to copy all but I need to copy 4000 of images and it would take an hour.

Dropbox sync folder on windows doesn't have similar problem. Looks like it doesn't deal with locking issue. Is it possible to deal with locks in different way? I mean obtain pessimistic lock, do the operations and release lock or take locks just on destination folder where I am copying files.

Unfortunately there isn't another way to handle this, but I'll be sure to pass this along as feedback.