In an ADA action, occasional delays in a good-faith negotiation are not a basis for equitable estoppel against deft's argument that the agency filing required by the statute wasn't timely.
http://media.ca8.uscourts.gov/opndir/18/06/171737P.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.