If you can not remove the executable bit on the scm then it might be worth deleting that file and get a new original then put that in the scripts folder.
The older version (no curved body) is here http://registry.gimp.org/node/20269
Very little point reinstalling Gimp (all platforms) as any problem often remains in the gimp profile which is not un-installed.
If you can not get anything working then a way of eliminating problems is rename the .gimp-2.8 folder (to say .gimp-2.8-bak) to disable. Run Gimp to create a new profile and start moving scripts in one at a time, checking as you go.
Since you recently moved from Windows to Mac, guessing the Mac filing system is a big hurdle
I tried all different ways earlier today to get that error, on layer groups / in layer groups / small layers / offset layers .... script worked every time.
The older version (no curved body) is here http://registry.gimp.org/node/20269
Very little point reinstalling Gimp (all platforms) as any problem often remains in the gimp profile which is not un-installed.
If you can not get anything working then a way of eliminating problems is rename the .gimp-2.8 folder (to say .gimp-2.8-bak) to disable. Run Gimp to create a new profile and start moving scripts in one at a time, checking as you go.
Since you recently moved from Windows to Mac, guessing the Mac filing system is a big hurdle
I tried all different ways earlier today to get that error, on layer groups / in layer groups / small layers / offset layers .... script worked every time.