Mistakenly marked as solved.
George, are you still having issues? I went back to this, and after all my research, my issue ended up being simple human error. I had my related field number wrong.
In the below example, my reference field was not 11, and I forgot to update it and it made it hang. All that, and it was a silly typo on my end. Now it works perfect and doesn't hang. Try checking that?
URLRoot()&"db/"&AppID()&"?a=dbpage&pagename=createchildsaveandedit.html&targetdbid="&[_DBID_Estimator]&
"&referencefield=11"&
"&rid="&[Record ID#]&
"&apptoken=xxx"
