BE 11d incremental backup missing files

Hi,
I have BE 11d on a Windows server 2003, and I ran 4 incremental backups (by modification date) Mon-Thu and a full backup on friday, now we noted that the incrementals backups are missing some logs files that only are backed up on weeken (full backups), there is no errors or warnings just the file is not backed up, this files are logs of Lotus notes, so had movements all time. Someones know what can be happens?

Thanks

Acisternas