I'm not sure about is preventing Windows from assuming MC is not responding and displaying the message box.
This is up to the people who know how to deal with Windows internals and know how to write code.
Let me add another case I experienced in the past and I just verified right now.
I just identified another case:
Load Full file into memory enabled, files stored on a NAS
I am playing a FLAC without problem, then, while playing, without waiting the end of the file, I switch to another file.
What happens?
While still playing the "old" file, MC starts to load into memory the new one and you can see the network usage to grow.
When the new file is finally fully loaded into memory, then MC stops to play the old one and switch to the new one.
So... when MC is in the middle, while still playing the old one but loading the new one, then MC GUI expands to the maximum, overlapping the Windows taskbar and becoming blurry.
Everything is restored when MC stops with the old file and switch to the new one.
If the above scenario is applied during the "Theatre View", in the theatre view appears the Windows taskbar and it disappear when MC starts playing the new file.
If memory playback is enabled, I do it because I do not want any disk or network activities during playback
If I switch track in the middle while playing, I pretend that MC stops playing the old file immediately, loads the new file and start playing it just when fully loaded, without seeming to hangs\crash
It is quite a nonsense the bahaviour we have now. At least put a switch in the Audio Options...