Annotate for InDesign works sometimes

This script should examine every rectangle in an InDesign document, then put a text frame in the upper left corner with the name of the graphic and the scale percentage it is used at. I already have “C=0 M=0 Y=100 K=0” as a swatch color.

This works sometimes, but I am stuck trying to debug this:

tell application "Adobe InDesign CS3"
	set frames to ""
	set myWindow to active window
	
	activate
	if (document 1 exists) then
		tell document 1
			tell myWindow
				set zoom percentage to 100
			end tell
			set AppleScript's text item delimiters to ":"
			repeat with p from 1 to count of pages
				tell page p
					repeat with i from 1 to count of rectangles
						set filePath to (file path of item link of graphic 1 of rectangle i) as Unicode text
						if filePath is not "null" and filePath is not "no disk file" then -- not tested
							set fileName to text item -1 of filePath
							tell rectangle i
								set {sc1, sc2} to {horizontal scale, vertical scale}
								set {x1, y1} to items 1 thru 2 of geometric bounds
								set y2 to ((y1 as real) + 3)
								set x2 to ((x1 as real) + 0.25)
							end tell
							set newTextFrame to make text frame at beginning with properties {geometric bounds:{x1, y1, x2, y2}}
							
							tell newTextFrame
								set fill color to "C=0 M=0 Y=100 K=0"
								set label to "annotate" & i
								set text 1 to ("" & fileName & " " & (sc1 as text))
								set applied font of text 1 to "Monaco"
								set point size of text 1 to 11
							end tell
						end if
					end repeat --frames
				end tell
			end repeat --pages
			set AppleScript's text item delimiters to {""}
		end tell
		display dialog "Done." buttons "OK" default button 1 with icon 1 giving up after 1
	else
		display dialog "Open a document, please." buttons "OK" default button 1 with icon 2
	end if
end tell

It stops at
set filePath to (file path of item link of graphic 1 of rectangle i) as Unicode text

Why? Any help would be appreciated.