System freezes after unhooking

https://github.com/katahiromz/msgscan
This is a test program msgscan (Windows message dumper; command line tool).
msgscan.zip

I have scanned the messages of the Shell_TrayWnd window as follows:

C:\msgscan> msgscan32.exe --class "Shell_TrayWnd"

Then I got msgscan.png. And then, I had pressed Ctrl+C to exit.
It freezed the system with an assertion failure as follows:

*** Assertion failed: pci->fsHooks == pti->fsHooks

***   Source File: ../win32ss/user/ntuser/misc.c, line 724

Why the system freezed?

The log: msgscan-log.txt