This error indicates that the pay amount provided states the amount of a specific non-network token more than once.
For example, the code below erroneously provides two tuples in the pay amount, both of which specify the amount of the same token:
A.pay([ amt, [amt, tok ], [ amt, tok ] ]);
You can fix this by deleting one of the tuples:
A.pay([ amt, [amt, tok ] ]);