Why liquid gun propellant proved troublesome

Did navies experiment with liquid gun propellant?

Yes. A Royal Navy demonstration is recalled as suffering excessive mixing that washed out the initiator; US Navy experiments are mentioned more tentatively.

The Royal Navy tried a liquid-propellant demonstration, and US Navy experiments are also recalled with less certainty. In the British example, excessive mixing washed out the initiating material. That created an ignition problem before any wider advantage of the liquid system could be realized. The weapon, date, and formulation are unspecified.