Screenshot including substile not working well

The “including substiles” option was added in an update to MPC. However, this new function still needs improvement.
When I choose “including substiles”, the output image only includes substiles, with black background instead of the video screenshot. I have tested screenshots on ass substiles, AVC and HEVC videos, via both hardware and software decoding.

Version information:
MPC-HC (Nightly, 64-bit)
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Build information:
Version: 1.9.21.40 (e50e4a6f1)
Compiler: MSVC v19.29.30143
Build date: Jun 14 2022

LAV Filters:
LAV Splitter: 0.76.1.3
LAV Video: 0.76.1.3
LAV Audio: 0.76.1.3
FFmpeg compiler: MinGW-w64 GCC 11.3.0

Operating system:
Name: Windows 8.1
Version: 6.3.9600 (64-bit)

Hardware:
CPU: Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz
GPU: Intel(R) HD Graphics 630 (driver version: 21.20.16.4508)

Will be fixed in next update.