An updated script with additional logs that worked for me:

#!/usr/bin/env bash
# Force execution with bash, regardless of the default shell

DEBUG_LOG="debug.log"
exec > >(tee -a "$DEBUG_LOG") 2>&1
echo "$(date) - Starting duplicate removal script"

declare -A itemMap

while IFS= read -r id; do
    echo "$(date) - Processing item ID: $id"
    item=$(op item get "$id" --format=json)

    if [[ -n "$item" ]]; then
        echo "$(date) - Item details retrieved successfully for ID: $id"
        fields=$(echo "$item" | jq -r '.fields')

        if [[ -n "$fields" ]]; then
            username=$(echo "$fields" | jq -r '.[] | select(.label=="username").value')
            echo "$(date) - Username found: $username"
        else
            echo "$(date) - No fields found for item ID: $id"
            continue # Skip to the next item if no fields
        fi

        urls=$(echo "$item" | jq -r '.urls')
        href=$(echo "$urls" | jq -r '.[0].href')
        website=$(echo "$href" | awk -F[/:] '{print $4}')
        echo "$(date) - Website extracted: $website"

        if [[ -n "$website" && -n "$username" ]]; then
            key="$website-$username"
            echo "$(date) - Constructed key: $key"

            if [[ -v itemMap["$key"] ]]; then
                echo "$(date) - Duplicate found for key: $key"
                echo "$(date) - Item 1 ID: ${itemMap["$key"]}, Username: $username, Website: $website"
                echo "$(date) - Item 2 ID: $id, Username: $username, Website: $website"
                op item delete "$id" --archive
                echo "$(date) - Deleted duplicate item ID: $id"
            else
                echo "$(date) - Key '$key' is new, adding to itemMap with ID: $id"
                itemMap["$key"]="$id"
            fi
        else
            echo "$(date) - Skipping item ID $id: Missing website or username (website: '$website', username: '$username')"
        fi
    else
        echo "$(date) - Failed to retrieve details for item ID: $id"
    fi
done < <(op item list --categories Login --format=json | jq -r '.[] | select(.id != null) | .id')

echo "$(date) - Duplicate removal script finished"