Sorry for the delay, my developer responded but I mixed up the threads and didn't know the response was for you. Here's what he said:
I don't get a 404 but the same page displays again and I found something odd outside of our plugin's scope: I was trying to diagnose the problem by adding some debugging output to the plugin so I went to the "Plugin Editor" (Plugins - Editor, admin side) to edit some files and when I clicked "Update File" I got a 404 error displayed (user side). This doesn't make any sense and has nothing to do with BD so I think something is off with some forms on this WP setup.
Trying to remove BD from the equation, I disabled the plugin and tried this again (editing any file through the "Plugin Editor") and got the same 404 error. This means BD is not the problem here.
I'd love to help the user but since I can't edit files to add debugging messages (because of said 404 error) I can't do anything further. What I can assure you is that it must be another plugin or something at the WordPress/Apache level. Or perhaps a memory/server issue.