What happened to Taranto's missing torpedoes?

Did some of the torpedoes launched at Taranto fail to explode?

Probably. Five of ten hit and detonated, one entered the mud, and the unresolved weapons suggest roughly a thirty-percent technical-failure rate.

Ten torpedoes were launched and five are recorded as hits that detonated. One more was found in the harbour bottom after an evidently bad entry. The other four were not securely accounted for and may have run outside the target area, buried themselves, or failed to explode. An approximate thirty-percent technical-failure estimate remains an informed judgment rather than a complete ledger. The uncertainty matters because wartime attack records do not always provide a clean success-or-dud result for every weapon.