Vuze often comes with adware that locks the proxy. Use a free cleaner:
Firefox can have its own internal proxy settings separate from the system. how to remove vuze webtorrent protocol proxy
Removing the Vuze WebTorrent protocol proxy can be a bit tricky, but it's a relatively straightforward process. By following the steps outlined above, you should be able to disable or remove the WebTorrent protocol proxy and resolve any issues you're experiencing. Vuze often comes with adware that locks the proxy