Why i got stuttering when interpolate to 2x

[brainplusplus]

Hi, i so confused, why my video got stutter when interpolate to 2x using audio

this is my command to generate output video :

butterflow -v -audio -r 2x "inputvideo" -o "outputvideo"

the output is here https://streamable.com/ne93x

the original video (input video) is here https://streamable.com/8dfy6

this is my spec (macbook mid 2015/MJLT2) :

OpenCL devices:
  Platform          	: Apple
  Platform Vendor   	: Apple
  Platform Version  	: OpenCL 1.2 (May 24 2018 20:07:03)
   Device 0    		: Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
      Version  		: OpenCL 1.2
      Version  		: 1.1
      Work Sizes	: 1024, 1024x1x1
      Compatible	: No
   Device 1    		: Iris Pro
      Version  		: OpenCL 1.2
      Version  		: 1.2(Jun 25 2018 19:28:16)
      Work Sizes	: 512, 512x512x512
      Compatible	: Yes
*  Device 2    		: AMD Radeon R9 M370X Compute Engine
      Version  		: OpenCL 1.2
      Version  		: 1.2 (Jun 29 2018 18:33:51)
      Work Sizes	: 256, 256x256x256
      Compatible	: Yes