quicktime resets playback speed after pausing
Here is an AppleScript code that will make QuickTime Player remember the playback speed of a video after pausing it. Go to Script Editor and paste the following code into a new document, replacing # with the desired playback speed.
tell application &quot;QuickTime Player&quot;
    set theWindows to windows
    set win1 to item 1 of theWindows
    tell win1
        set visible to false
        set visible to true
        set index to 1
    end tell
    tell document 1
        repeat while miniaturized of win1 is false
            if playing and rate is 1 then
                set the rate to 1.5 as real
            end if
            delay 1.0E-3
        end repeat
    end tell
end tell

The playback speed (&quot;#&quot;) can be any real decimal number (i.e., 1.5). Values larger than 1 will speed the video up, and values between 0 and 1 will slow the video down. A negative value will cause the video to play backwards.
Note: The audio will drop out at speeds less than/equal to -2 or greater than/equal to 2.
Press Command+S (or File &gt; Save) to save the script in a location where you can easily access it, and then open the script and run it (press the Play button at the top) whenever you need it. You can pause and play the video as many times as you want, and it will play at the selected speed each time, as long as you do not minimize the QuickTime Player window. You can resize and move the window, and also open other applications in the foreground, though. When you are done, click the Stop button (to left of Play button) and you can close the script.
It can be a little buggy at times, but this is the only method I have found to remedy this issue.