Garbage Characters Appearing at Beginning of Output in Whiptail Textbox

Question

I have a function block that runs an Expect script, pulls the output, tweaks it through a combination of tr and grep to pull out the specific line of text I am looking for and then displays the text in a Whiptail textbox. Everything works fine except the beginning of the output in the textbox; it contains characters that are not in the actual variable that is being outputted.

The function block I have is:

do_view_URL() {
        NODE="$PROPERTY_IP""$TOTE_BOARD_IP"
        OUTPUT=""
        OUTPUT=$(/usr/bin/expect /home/pi/ssh_tote_board_url_grab.sh $NODE)
        CURRENT_URL=$(echo $OUTPUT | tr -d '\r' | tr ' ' '\n' | grep https: | head -1)
        echo $CURRENT_URL
        echo $CURRENT_URL > ./textbox_file
        whiptail --title "Current Production URL for Tote Board #$TOTE_BOARD_NUM" --textbox ./textbox_file 10 150
}

The Whiptail textbox output looks like this:

Whiptail Textbox

At the beginning of the output, the following characters appear; the characters are always the same no matter how many times I run the script:

^[[?2004l

As you can see in the function block, I am also outputting the value of "CURRENT_URL" to the CLI. The results of that as well as a cat of the ./textbox_file are as follows; clearly the garbage characters do not appear in either the echo output or the cat output:

pi@XXXXXX:~ $ ./tote_board_updater.sh 
https://<REMOVED>
pi@XXXXXX:~ $ cat ./textbox_file
https://<REMOVED>
pi@XXXXXX:~ $

Any help, assistance, or guidance as to where these characters could be coming from and how I can get rid of them in the output so that the end result is that the output is just the full URL would be greatly appreciated. Thank you in advance.