It doesn’t necessary have to be half a second, second or two should be fine.
There are two likely failure points here for the simple XT-90s loop key melting:
1 - not plugged all the way in. That small resistor doesn’t stand a chance of handling the full load. Poof! Especially when new these suckers are TIGHT and can be tough to seat fully.
2 - they fail. simple. They are made cheaply and if one misses a good QC and has an issue - it’ll still fail if everything else is still correct. My assumption of your issue @DeathCookies.
Orientation should not matter. Period. If you did not fully kill it and swapped orientation and it worked i would then suspect some soldering issue or similar. But most of the time it will die if it goes - and a new XT-90s that works in the other orientation may seem like the fix, but i’d be willing to bet you a shiny nickel if you swapped it - it would still work.
Still one of the easiest and cheapest ways to suppress the spark. Definitely worth getting a few spares just in case.