The command did heavy work before replying and went past the three seconds Discord allows for a response.
In large servers the command did not respond. Roles were not returned, or it was unclear whether they had been.
It now replies first and works afterwards, and any failure is written to the log.
Nothing sits between receiving a long command and replying to it.
Fixed: the command responds right away and hands out the roles afterwards.
When returning roles to the whole server, Discord shows "The application did not respond".
Every incident that lasts 15 minutes or more, or is serious, gets a public report within 48 hours.