Backup to Dropbox fails for large sites

SYSTEM INFORMATION
**OS type and version: Centos 8 REQUIRED
**Webmin version: 1.981 REQUIRED
**Virtualmin version:6.17 pro REQUIRED
Related products version: RECOMMENDED

My backups keep failing. We use dropbox as a backup destination and most sites do not have a problem. Only a few of the larger sites (> 20gb) fail. Backups take around 15 hours before failing with the following error:

Uploading archive to Dropbox ..
.. upload failed! HTTP/1.0 429 Too Many Requests (performed 3 attempts)

Total backup is around 200gb for all sites. Is this a limitation with Dropbox? Is there anything I can configure to fix this?

According to their website, the largest file size allowed is with the Professional Plan ($16.58 per month) and is 100 GB.

Elsewhere though the max file size is listed as 50GB.