Grant837 on "Incremental local backups are doing full backups of unchanged files"

Hi, I have a local back up to a mapped drive for 677GB. The last backups have been shown as failure, but I can see its only one file. Yet, when my scheduled backup starts, many files that I know 100% for sure have not changed, go through a full backup again. It is at least 185GB of files on last check... its doing it again now (for 2 hours and is at 37%) and I will see if its the same volume and/or files.
Any idea what is going wrong?