Splitter Controls Sometimes Hang In Fixed Position

Moving a Splitter in the UI at Slow or Normal speed seems OK.
When I move the top Vertical slider Left or Right quickly to just “slam” into the Left or Right side
the position of the small graphic of the is no longer responsive.

I have reproduced by “slamming” either the Left or Right side or to the Top.

Also I was able to move the Horizontal Splitter up and down and when I then Slammed the Top the graphic wrapped around to the middle of the screen but could no longer be moved.
(Perhaps a coordinate wrap around ?)

This can be reproduced by also using the Playground on my browser.

Perhaps this is a Timing problem?
Running on Firefox (latest) on Win10 2GHz 4 core i7 8 GB RAM
or running just JS as HTML on Firefox or Chrome or Edge.

Because I think there may be a Timing problem, I did not try to simplify as that may have hidden the problem.
Below is way to reproduce:

<?xml version="1.0" encoding="utf-8" ?>
    <splitter direction="horizontal" width="100%" height="30%">
        <box width="50%" height="100%" style="background-color: #FF00FF;clip:true;">
            <textarea id="output" width="100%" height="100%" text="1 2 6 24 120\n" />
        <box width="50%" height="100%" style="background-color: #FFAAAA;clip:true;">
            <textarea id="otherInfo" width="100%" height="100%" text="\n Other information:\n" />