The bug can be reproduced by running a test script that simulates successive key presses in sequence at high (touch-typing) rates. The attached screenshot shows the local copy of that script in the top half and the key presses as they appear in a terminal window on the remote machine in the bottom half. The annotations show that there is on average one reordering every 7-8 closely timed keystrokes.

testcase-annotated.png

The script code is (you may have to run pip install pyautogui to install the dependency into your python interpreter):
import time
import pyautogui

time.sleep(5)
for k in range(10):
    pyautogui.press(list('0123456789abcdefghijklmnopqrstuvwxyz'))
    pyautogui.press('enter')
    time.sleep(1)

Note that the editor is PyCharm (a popular Java-based IDE), which is a bit more CPU-intensive than some other software during editing, so this could well have something to do with it. If you want to test it with that, PyCharm is freely available from: https://www.jetbrains.com/pycharm/

Thanks for your attention,
Christian