I think 3 times the HR canister leaked and all the gas came out while I was out in the backcountry. The other zillion times no problems.

Anyway, the FAA made that type of (rubber nipple) can illegal on air travel due to leakage in the baggage compartment. The companies making the fuel canisters shut down to avoid lawsuits. Coleman had camping stoves (model 5404) that used them.