Hasty Declarer Play
Declarer wins the first trick, leads Ace-trumps to the second (all follow), King-trumps to the third (LHO and dummy follows, RHO considers their discard).
Realising it was a 3-1 split, declarer then prematurely leads Queen-trumps and LHO mindlessly follows. Hearing the request for another card from dummy, RHO cries foul, and calls the TD.
Law 67B1b - Defective trick, failure to follow is deemed to be a revoke, one trick penalty and put a card down.
But hang on, says RHO, I've done nothing wrong and I'm being penalised. Surely Declarer's premature lead is the issue? But no, says Declarer, LHO accepted it. Well what about Law 72C then, says RHO in desperation?