I just upgraded to Forms 10.4 and have been using "onloadlookupfinished" just fine in 10.3.1 in conjunction with several rules that fill several different tables. 

After going to 10.4, "onloadlookupfinished" is firing correctly if the Lookup Rules that fill the tables are returning a value.  The issue is that if any of the tables do not have values yet, it never finishes loading.  I verified by putting an alert in JS in "onloadlookupfinished". 

    $(document).on("onloadlookupfinished", function(event) {
    alert('Hi');  
    });

When the rule that had 0 returned results was

• Enabled, the alert never popped up
• Disabled, the alert popped up
• Updated to have 1 or more returned results and was enabled, the alert popped up

Anyone have any ideas or has run into a similar issue?