Hmm, apparently that option was added post 6.0.1. Thanks for the screen captures and the careful attention to detail.
SLAMM 6.2 will come out in early December and will be 64 bit. Just need to finalize some documentation.
I will email you an interim version which allows Bruun to be turned off to see if that solves the problem.
The only thing I can think of is if your beach is on a thin strip of land that SLAMM sees as a barrier island (<500 meters between the front edge and open water or back-edge marsh) and your frequency of barrier island overwash is set fairly high. That would erode a lot of beach.
Unless you send me your study files directly (email to firstname.lastname@example.org
) I can't help you debug your problem. Hopefully the version of SLAMM I send you will help shed some light as you can turn Bruun off and see if it's still happening.
Cheers -- Jonathan