Can not find version 1 you may have deleted it back up fails

Hi

Just getting used to this back up programme.

I ran a incremental file backup on several folders on my sysstem.
I back up to external USB drive.

The shedul arrived today for the 2nd incremental backup.

However it failed :( the whole back up that is because it looks like it could not find some files on the source!
Well, due to normal house keeping I have deleted some files, but also added quite a few.
Attached is a screen shot of the log.

Is it going to be the case that I need to make a full backup every time or am I missing a setting?

Thanks