There is a bug within all offical versions of Scratch on all platforms that maninfests itself badly on low power devices such as the RPi.
MathsWhizz from the Scratch forums has developed a solution which only just involves a few small changes to the Scratch.image. A modified image for use on Raspbian based systems is available to download here
So, your Scratch.image file is situated in the
To avoid any issues, make a backup copy by using LX Terminal and typing
sudo cp /usr/share/scratch/Scratch.image /usr/share/scratch/Scratch.orig.image
Once this is complete, all we need to do is copy the downloaded image and overwrite the default one
sudo cp /home/pi/ScratchM.image /usr/share/scratch/Scratch.image
The modifications do nothing else than stop the variable values being updated on the screen unnecessarily . No changes are made to any of the core code of Scratch and any Scratch scripts created with this version of Scratch are identical to any scripts produced by the default Scratch image.
Back to Scratch page http://elinux.org/Scratch_on_RPi