Wireshark has no way to properly cleanup in extcap plugin on Windows
Right now, extcap process has no way to cleanup gracefully when stop capture in Wireshark on Windows because Window seems not support SIGTERM.
Links / references / protocol specifications
The SIGKILL and SIGTERM signals are not generated under Windows. They are included for ANSI compatibility. From MSDN
The open questions are asked by Wireshark contributor
How to properly finalize capture in a Wireshark extcap plugi
what is the best way to clean up in extcap?