Upload multiple files in session

MatthiD, I'm glad to hear you were able to find a solution for your use case.

To clarify, there are different types of 429 errors. It is always recommended to log the error message that accompanies an error code to get a better idea of what may be happening with the request.

To help avoid a potential lock contention error (429 too_many_write_operations), which might have been the case here, an upload session operation is recommended because of the way it handles uploads — as described in the Performance Guide:

Each file upload to Dropbox consists of the following stages: appending the byte contents of the file to an upload buffer on the Dropbox server, obtaining a namespace lock, and then committing those bytes as a file into a target namespace. The /files/upload endpoint does this atomically, whereas upload session decouples these steps.