I got this for my BPM 3800 to make my own.
Not sure if its going to work was a gamble but here is the unboxing and Teardown. The Teardown starts at 8min 30seconds to find the rattle.
Blog Post with More Photos.
https://www.stevenrhine.com/?p=134893 Will do a second video on the main board. prob publish it Sunday/Monday.