Applescript debugging PLEASE HELP

So I wrote this automator program that basically takes a list of sequences and inputs them into a server and appends a URL on the page into a text document

It works perfectly for a couple and then randomly just stops working and it is driving me craaaazy . i've been trying different delay times but just can't seem to figure out the problem.

so before this applescript there is a for loop then sends all the sequences to it one at a time .

1st) tabs to the text box

2nd) pastes the sequences into the text box

3rd) tabs to the Proceed button

4th) presses enter

5th) on next page, it grabs the URL that is specified at a certain position

the bug randomly happens after it pastes the sequence into the box and then it will randomly go to the URL bar at the top of Safari and get stuck doing weird things over there . this throws off the whole flow of everything ?

I REALLY want to know why this is happening ? Why would it work for like 3 or 4 andf then act up on the next one when the format for the sequences are all the same ? Do I increase a delay at a certain position ? I think one way to bypass this problem would be to tell applescript to press the proceed link" does anyone know how to do this?

delay 1

tell application "Safari" to open location "http://rna.tbi.univie.ac.at/cgi-bin/RNAfold.cgi"

delay 5

tell application "System Events"

key code 48

key code 48

delay 0.5

keystroke "v" using command down

delay 4

key code 48

key code 48

key code 48

key code 48

key code 48

key code 48

key code 48

key code 48

key code 48

keystroke return

end tell

delay 5

tell application "Safari"

set thelink to do JavaScript "document.links[4].href " in document 1

end tell