Know its an alpha so unsure how much you are looking for bug reports at the moment, as maybe you already have a big list of known issues
When using Linux on selecting a file to open the file browser opens fine for selecting a file, seems to crash (lockup) once a file is selected. I have recreated this on 2 diffrent installs (fine on 1.3 and Windows when using alpha).
Here is the process that seems to cause the lockup:
11290 ? S 0:00 sh -c (while ! wmctrl -F -a "Open" -b add,above;do sleep 0.1;done) & (WINDOWID= && zenity --file-selection --title="Open")