This may be a known problem when add child on a cross app relationship.
I seem to recall also suggesting tom someone else on the forum try this trying this but it did not work but you can try and let me know.
var text AddChild =
URLRoot() & "db/bkfza5uhh?a=API_GenAddRecordForm&_fid_19=" & URLEncode([BF RO #]);
var text DisplayParent = URLRoot() & "db/" & "?a=dr&rid=" & [Record ID#;
$AddChild
& "&NextURL=" & URLEncode(DisplayParent)
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Mark Shnier (YQC)
Quick Base Solution Provider
Your Quick Base Coach
http://QuickBaseCoach.commark.shnier@gmail.com
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