Declarer has two cards left, trump ace and high card in another suit.
Claims last two tricks, no explain.
Defenders reject, since one outstanding trump. Declarer continues with trump ace. Defenders refuse to continue to play, and get TD to adjust to only 1 of last 2 tricks to declarer.
Agree with TD decision?
How about if a defender, when rejecting, states openly "I have a trump"
About claims (Law 70 - 1997):
Quote
When a trump remains in one of the opponents’ hands, the Director shall award a trick or tricks to the opponents if:
1. Failed to Mention Trump
claimer made no statement about that trump, and
2. Was Probably Unaware of Trump
it is at all likely that claimer at the time of his claim was unaware that a trump remained in an opponent’s hand, and
3. Could Lose a Trick to the Trump
a trick could be lost to that trump by any normal play.
...
From the the purposes of Laws 69, 70, and 71 , "normal" includes play that would be careless or inferior for the class of player involved but not irrational.

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ing) tr. v. - Any bid made by bridge player with which partner disagrees.