> when I inverted it, the fuel leaving the can made the valve freeze
This is possible, but rather hard to do deliberately. Normally the fuel goes down the hose as a liquid and vaporises in the preheat tube near the burner. For it to be vaporising at the valve on the canister is odd.
What to do if this happens? I'm not entirely sure as I have not had this problem more than once or twice. I THINK what I did was to open the valve up for a moment, to overload the system and force liquid fuel down the hose, then shut it down to a gentle flow again quite quickly. Once the hose is full of liquid fuel all seemed to be well.
But I am not recommending that you should do this, just saying what worked for me. Experimenting like this has a few hazards... big ones.
If the stove continues to behave like you described, I would return it for exchange, as it just may be that the hose is missing the filler cord which is meant to be inside it. Once again, I am not sure about this.