Have had contact with the developer and i can now confirm that it is now fixed in 5.1.0.2825 version released yesterday.
Works flawless now. Great job!

If you do encounter this again, please capture this in a debug log (step 4b) and attach the log to a Support Ticket: https://www.mediamonkey.com/forum/viewtopic.php?t=86643

This will help a developer analyze why this happens on your setup.

out_WASAPI.dll
This was a mp3 file.
It does not apear to be a track issue, when i now replay the song all is Ok.
https://youtu.be/MxR1lpLXqac

Which [url=https://www.mediamonkey.com/wiki/WebHelp:Player/5.0#Configuring_Output]Output Plugin[/url] and what File Type(s) are causing this for you?

Since i installed beta 5.1. I see from time to time the DOT from the progressbar flipping to starting point and then going back to the right position. Not really an issue as sound is playing Ok.

Have seen this happen on 2 of my computers. It happens less on a fast computer. And see it happen more on a slower computer.

See video;
https://www.youtube.com/watch?v=yLjHWUDP2lQ