soundconverter pause conversion while still consumming cpu but continues afterwards when I scroll to the file

I batch 260 m4a (aac) file to be converted to mp3
the 50 or 100 files or converted but all of a sudden it stops conversion.
No new file is created on disk but sound converted still consumme cpu not 100% on all core but may 50% or 100% on one core

It stays like that more than one hour
and when I went back to soundconverter and scroll to the last file converted in the GUIi, the conversion procress restarted as soon as the next file to be converted was visible in the GUI. I was able to see immediatly 2 progress bar to fill for the next 2 files beginning to be converted.

To reproduce that you need add many files using "add directory" and don't scroll at all in the GUI. And wait ...

Finally it crashed with a gtk error bug I have already reported.