Windows does it not sure why the difference in drivers for front and rear headphones but maybe yours goes to the wrong one? Or gets stuck in transition.

I'm not how sure how this can be possible. I'm using the default Windows audio driver.

when you place in headphones windows automatically changes sound drivers to the headphone drivers,
this might be the reason for the loss of connection to mm.

suggestion try updating the sound drivers

v4.1.11.1783. I think this is easy to reproduce. Try this:

A) Connect external headphone to laptop
B) Play a song
C) Open playback device window
D) Right click on Headphones and click disable. This will do the job. If don't repeat enable/disable on headphones option few times

Sometime it temporarily stop the playback. Sometime it even crashes the window

Which version of MediaMonkey?

If I change the playback device using the settings, or insert/remove earphone from the connector, MM several time get unresponsive. Sometime it continue playing the song, without any sound. Sometime it loop back repeatedly a part of song.