Akuhn & DND ON,
The only timers that should affect it you have already changed. The Abandoned Call timer shouldn't even come into play or some of the calls would have been picked up by the users attendant.
At this point I would look more at the software version as an issue since it isn't working as expected. This is assuming that it is setup correctly.
What happens if you forward a call instead of using DEE?
Thanks,
TE