Autobackup problems

some time ago i installed autobackup, and since then the backups keep getting bigger and bigger and bigger and…
in the beginning the backups were about 100 MB, by now that has increased to more than 600 MB.
what’s going on? and what can i do about it?

many threads about what could cause this. here’s one:

This is a recent thing, you may have this problem as well.
Disk space being eaten up - #9 by mjvanderveen.