We consider bipartite LOCC, the class of operations implementable by local quantum operations and classical communication between two parties. Surprisingly, there are operations that cannot be implemented with finitely many messages but can be approximated to arbitrary precision with more and more messages. This significantly complicates the analysis of what can or cannot be approximated with LOCC. Towards alleviating this problem, we exhibit two scenarios in which allowing vanishing error does not help. The first scenario involves implementation of measurements with projective product measurement operators. The second scenario is the discrimination of unextendible product bases on two 3-dimensional systems.
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