dmcgynn - I was thinking the same thing!
My newf started this on walks when she wanted to be in charge and take the pace. When I would hold her back, or check her, she'd stand up on her back legs and box with me, then drop and lay. Then as soon as she'd get up (after a minute or so) she'd start pulling again. Of course she'd do this out on main street in town.
After she did this several times and being completely bewildered
on how to handle this, and knowing she was only trying to get the upper hand. I took Jeannie's advise about handling aggressive dogs, and I quickly laid on her holding her down. She immediately tried to get up, and I made her stay down until she was completely still and quiet for several minutes.
When I let her up, she healed very well and NEVER has pulled that drop and flop routine on me since.
Just my two cents.