Thanks for your feedback Steve. That was the same assumption I had, until I upload a lot of data, the backup failed because MSP360 maintenance window was in the middle of uploading 2-3TB of initial data.
I opened a support ticket and that's the reply I had once I questioned about why it didn't left of where it was and why it was starting a new full backup, meaning that all the days I had sent data was going to the trash:
"If the backup fails, it needs to be started anew (just the latest run, not the whole chain), leaving the data that was uploaded on the storage and marking it as a failed incremental run. The backup can not be continued, from the same spot, neither in legacy nor in the new backup format plan.
What actually happens when the incremental backup fails and we start a new backup run: The software checks if the previous backup execution was successful or not and most importantly if the restore point created during the previous backup execution is valid. If the restore point due to backup failure is invalid the software looks for the last valid restore point before it. When the valid restore point is finally found, the software starts listing the information about the data that is on the machine and in the cloud. Once this is done it starts the upload of the data. (some steps like shadow copy creation are skipped to shorten the description of the process)."
That said according to the screenshot you have provided, the full backup run failed and the last restore point before the full was in a previous chain, hence all your current incrementals that were successfully uploaded belong to a previous backup chain. (the last successful full backup)"
Later I questioned about if the first full backup fails and would it reuse the data...
"Unfortunately no, since the shadow copies are different, and the data on the storage might have an unfinished upload which means that the file is basically useless since part of it is missing. There is a way to use the data that is on the storage already, but it requires a few things such as a successful first full backup and Backup storage that supports synthetic backups. You can read about this option here: https://help.mspbackups.com/backup/about/backup-format/synthetic-full-backup""
about the Synthetic Full, I'm aware and that's wonderful as it doesn't cost as well.