Can't Re-Save on Mac


I have been trying a development snapshot version of Synfig Studio version 1.3.3 and having great difficulty saving my work.
I am using a Mac with OSX 10.11.6 (El Capitan)

If I only use the Spline tool, saving seems to function normally, however, as soon as I use any of the drawing tools, such as; Draw, Brush or Sketch I run into problems saving my edits.
The first save seems to work ok and an associated .png file seems to be automatically saved along with the .sifz file, however I have noticed that the .png files are empty of any drawn data and are always the same size no matter what. 267 bytes.

Are there any Mac users here that have these problems ?
In my forum searches, I have not seen many posts by Mac users since 2015 or so. Perhaps this is the reason why ?
I explored the github site for any related issues and saw nothing there either.

Note; I Re-Installed version 1.2 and noticed the same problems.

Thanks for any comments or advice.