Have you found that with the Numbers update from April 1st, Apple broke documents?
///// fails with 3.2, worked in 3.1 /////
choose file with prompt "Choose Numbers file "
set files_to_get to result
tell application “Numbers”
open files_to_get
set thisDocument to document 1
end tell
Result:
error “Numbers got an error: Can’t get document 1.” number -1728 from document 1