From a recent team match, South was declaring 5♦X.
In the above position North lead 7♣. East ruffed with 7♦ and claimed 2 tricks. (Possibly meaning 2 more in addition to this trump trick).
West wished to contest the claim ie wanted 3 tricks but had no mechanism to do so.
By the time he had typed his objection Declarer had accepted the claim.
In accordance with L68B2 if a defender attempts to concede one or more tricks and his partner immediately objects no concession has occurred.
I therefor believe that for a defensive claim there should have to be acceptance by Declarer AND THE OTHER DEFENDER.
I would welcome opinions on this suggestion