Scheduled Backsups to Amazon S3 not always working

I have two scheduled backups for all my servers…
FULL backup to run every Sunday
INCREMENTAL backup to run every day

I have not checked all incrementals but the ones I checked seems to be there.

Theissue is with the FULL. I noticed on a couple of servers, recent full backsups for the last week or two were not there. Last full backup on one server is 2nd March, and today its the 26th.

Another server looks to have the full backup but when I go into the folder, there are only two virtual servers in it, but there should be about 20. The week before has all virtual servers.

I just wondered what could be causing this issue?