Unfortunately it seems that the latest version has introduced some instability in the "Play to Speakers" function, or more accurately, stopping the playback. It seems to be inconsistent (so hard to replicate an exact set of circumstances) but reasonably common to get some kind of pointer errors when stopping playback.
Here's one I got just now:
A fix would be awesome.Exception EInvalidPointer in module SynthFont2x64.exe at 000000000141B38.
Invalid pointer operation
Thanks for your hard work.