This sounds like a bug in documenso then if it can't find expected objects in the storage. But if we want to investigate here, maybe not use a Beta S3 storage on top of a feature in Documenso for a start.
@kbtonmoy how are you configuring Documenso? Is this the S3 backend configs around NEXT_PRIVATE_UPLOAD_BUCKET around https://docs.documenso.com/developers/self-hosting/how-to#advanced-configuration ? Have you already looked for help from Documenso as it most likely is not a Cloudron related issue.