I won't speak for my thoughts on warranties and things. But orthrodynamics I'd imagine are robust to drops. Mechanically they are very very simple. A semi-metalic diaphragm stretched infront of some magnets....
But keep trying with Hifiman..
If worst comes to worst and it really really does come down to a hard no from the company and you're stuck with them, not all is lost. You're in a good community here on headfi.
I don't think it's unfixable thankfully. I have opened my 4xx up and they seem very simple inside.
So exhausting the warranty route, here are some tips speaking from my T50RP modding experience: obviously this is at your own risk. I don't suggest opening them unless you are comfortable with the fact they are delicate and easy to break if you poke the wrong thing, and that's on you if you do. Once they are opened, many companies will say this voids your warranty
1: Simple first, the cable itself, not the headphones. Swap the cables to the other ears, if the problem switches, whelp it's your cable. Or you can use a multimeter to check continuity
2: Start moving up the line. Not the cable? Maybe the connector in the can. A pin may not be making good contact, might just need to be bent back into place
3: Check the wires on the inside. First the wires on the plug, then follow them up to see if they got pinched anywhere. I believe mine had pinched wires (but didn't do anything, just something I saw). If they are badly pinched, multimeter to check the continuity on the individual wires. Replace the wires if necessary.
4: Look at the solder to the pads of the diaphragm. Sometimes cracks in the solder allow it to be loose, but still attached. Reflow if needed. Be careful. Diaphragms are very thin, very easy to melt.
5: Try and look at the traces. Basically a last ditch effort. Even if you find it, if it's deep into the diaphragm circuit, there isn't much that can be done at that point.