Hello,
Miraheze is making some infrastructural changes (i.e. migrating to new servers). There may be multiple issues for a week at most or around another 48 hours at least. We are experiencing issues with file uploads and thumbnail rendering failing currently. Thank you.
Please also note that extreme slowness and frequent 502 Bad Gateway errors are expected as well.
These issues have now been fixed. We are waiting for Miraheze to move us to their new file servers now.
The file servers have been migrated yesterday as well. There were some issues with database backups not working but they have since been fixed. Some other changes have also been made which have caused periodical extreme slowness.
Most other servers have been migrated as well. Please note that North American users will soon start facing slower load times.