The message:
"Cannot perform stat(): ([2] No such file or directory) => not backed up"
can be generated for one of 2 reasons
When a Backup starts, DP does a 'treewalk' where it builds a list of files and directories to be backed up. Then the actual backup starts. If any of those files were deleted between the Treewalk and the Backup, you will get this warning
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In your backup specification, you may have specific files indicated in the Include part of Trees/Filters, which is only accessable in the Backup Object Summary. If you are Including a specific file even if using Wildcards such *, and the file is not there, it can generate this warning.
If you think that it may have something to do with the lag between backups, I would think that running a Full Backup will clear this up, but, in my experience, I have never seen this warning generated for this condition
Finally, keep in mind that this is just a Warning, and, hopefully, will not keep your backups from fiishing