Incomplete files written to root dir

[wiggins09]

Some files are being written to the root of the download dir when I am using assemble incompletes. These don't appear to be all the incompletes selected for rebuild & sometimes sfv or pars that are not damaged are also present.
The files are from nzb sets being downloaded to ..\$(NZBFILE)\

Currently when I am seeing incompletes NBP seems reluctant to assemble using pars & will wait for the full files (sometimes for 1hour+). I have aggressive checked.
I have then manually calculated that if the pars are available there is enough to complete the package, & tell it to assemble incompletes.
The rebuild in this instance works but I then have files scattered on the root of the dir, these are incompletes from the selected nzb.

(Using W7 & nbp 6.60 b4163 x64)

Thought you would like to know