Epic Scrabble endgame between decades-long friends and rivals

Few players have been at the top of the Scrabble scene longer than Joe Edley and Jerry Lerman. Both have been high-ranked experts for over 40 years, and Joe has won three National Championships, with Jerry finishing near the top at many of them himself. Joe and Jerry have played many times in tournaments, but they're also good friends and have played hundreds, if not thousands, of online games. One recent game they played on the Scrabble GO app stood out for its fiendishly complicated endgame. Joe sent me the position, and we thought we had it solved with our collective efforts. But a run through the Macondo engine proved us wrong: we had missed a key detail! What was it?