The whole game crashes at least 80% of the time following a ranked match with the message “The software was closed because an error occurred”.
There is a current bug on the Switch version which can cause ranked matches after your first one to error out. The patches have already been deployed to the PS4 and PC versions, but Nintendo’s policy delays patching by anywhere from 8-20 days. In order to work around the issue, you will need to restart Fantasy Strike after every ranked match, unfortunately 
Does the patch fix the problem where the game crashes during the daily challenge? I haven’t been able to play the daily challenge at all because it keeps crashing about 15 seconds into the first match. This has been going on since last week
That’s a good question. I do not know. That would be a question that @Thelo may be able to answer.
The crashes on the menu screens during ranked matches will be fixed in the next patch. This was already hotfixed a while ago on Steam and PS4, but Nintendo patches take 20 days to approve because of Nintendo’s policies on patches.
The issue occurs when you play 2 or more ranked matches without restarting the game. So for the next few days before the patch, you could use the workaround of playing 1 ranked match, restart the game, play another ranked match, etc. We hope the patch gets approved soon…
I’m still having the same issue after the update. The changelog mentions a crash was fixed on the character roulette screen, but where it’s been crashing for me is after the entire match is done.
I’ve been having crashes after online play on Switch too, generally when I’m matched with an opponent during survival mode.
I recently bought the game on sale so the latest patches should be installed but I’m still experiencing a ton of crashes, usually before a ranked match starts.