RubyMine stop button creates zombie Puma servers in Rails app

Question

Specifications

Windows 10 (10.0.17134 Build 17134 with Feature Update 1803) running Ubuntu 18.04.1 LTS via Windows Subsystem for Linux
RubyMine 2018.2.3
Puma 3.12.0
Rails 5.1.4
Ruby 2.5.1p57

Issue

Starting a development environment with the green start arrow in RubyMine starts a Puma server as expected. The server console log shows:

]0;Ubuntu^Z
=> Booting Puma
=> Rails 5.1.4 application starting in development
=> Run `rails server -h` for more startup options
[2331] Puma starting in cluster mode...
[2331] * Version 3.9.1 (ruby 2.5.1-p57), codename: Private Caller
[2331] * Min threads: 5, max threads: 5
[2331] * Environment: development
[2331] * Process workers: 2
[2331] * Preloading application
[2331] * Listening on tcp://127.0.0.1:3000
[2331] Use Ctrl-C to stop
[2331] - Worker 0 (pid: 2339) booted, phase: 0
[2331] - Worker 1 (pid: 2343) booted, phase: 0

(Not sure what's with the broken characters around Ubuntu at the top, but that's another issue...)

I can monitor the server by issuing the ps aux | grep puma command in console. The output is as follows:

samort7   2456 16.9  0.3 430504 66420 tty5     Sl   23:58   0:05 puma 3.9.1 (tcp://127.0.0.1:3000) [rails-sample-app]
samort7   2464  1.6  0.3 849172 54052 tty5     Sl   23:58   0:00 puma: cluster worker 0: 2456 [rails-sample-app]
samort7   2468  1.5  0.3 849176 54052 tty5     Sl   23:58   0:00 puma: cluster worker 1: 2456 [rails-sample-app]
samort7   2493  0.0  0.0  14804  1200 tty4     S    23:59   0:00 grep --color=auto puma

Clicking the red "Stop" button in IntelliJ causes this line to show up in the server console log:

Process finished with exit code 1

However, running ps aux| grep puma again reveals that the puma server is still running:

samort7   2464  0.2  0.3 849172 54340 ?        Sl   Oct12   0:00 puma: cluster worker 0: 2456 [rails-sample-app]
samort7   2468  0.2  0.3 849176 54332 ?        Sl   Oct12   0:00 puma: cluster worker 1: 2456 [rails-sample-app]
samort7   2505  0.0  0.0  14804  1200 tty4     S    00:01   0:00 grep --color=auto puma

Repeatedly clicking start and stop will cause more and more zombie processes to be created. These processes can be killed by issuing a pkill -9 -f puma command, but that is less than ideal and defeats the whole purpose of the stop button.

Expected Result

Running the server directly from the terminal with rails s -b 127.0.0.1 -p 3000 starts the server as before and then pressing Ctrl+C gives the following output and doesn't create zombie processes:

[2688] - Gracefully shutting down workers...
[2688] === puma shutdown: 2018-10-13 00:12:00 -0400 ===
[2688] - Goodbye!
Exiting

Analysis

According to the RubyMine documentation, clicking the stop button:

invokes soft kill allowing the application to catch the SIGINT event and perform graceful termination (on Windows, the Ctrl+C event is emulated).

Despite what the documentation claims, this does not appear to be happening. It seems that the stop button is actually issuing a SIGKILL signal, stopping the process without allowing it to gracefully clean up.

I have also noticed that if I close all terminal windows both inside and outside of RubyMine, then open up a new terminal window, the zombie processes are gone.

Question

How can I get RubyMine to issue the correct SIGINT signal upon pressing the red stop button so that the Puma server can be shut down gracefully without creating zombie processes?

For reference, I am experiencing this issue in this commit of my codebase (a chapter from Michael Hartle's Rails Tutorial).