***** if (self.activateCount > 0 ) { ********

http://mbientlab.com/community/search?Search=activateCount

        self.activateCount--;

"Assertion failed: (self.activateCount >= 0), function -[MBLRegister deactivateAsync]_block_invoke, file /Users/macbookpro/Desktop/ZFitnessTracker/METAWEAR_code/LATEST_Metawear_swift_edit/

After a little debugging, it seems that deactivateAsync is called, but activateAsync is never called.  So activateCount becomes -1, instead of balancing out like it is supposed to.  (found in file MBL

self.activateCount--;

Assertion failed: (self.activateCount >= 0), function -[MBLRegister deactivateAsync]_block_invoke

Assertion failed: (self.activateCount >= 0), function -[MBLRegister deactivateAsync]_block_invoke

Assertion failed: (self.activateCount >= 0), function __30-[MBLRegister deactivateAsync]_block_invoke, file /Users/dad/Dropbox/Projects/mbient/MetaWear-SDK-iOS-macOS-tvOS-master/MetaWear/Classe

Assertion failed: (self.activateCount >= 0), function __30-[MBLRegister deactivateAsync]_block_invoke, file /Users/sschiffli/Code/metawear-ios-api/MetaWear/MBLRegister.m, line 572.