I use 2 main registrars for domain registration. The registrars are fairly big and their infrastructure is reliable. Still in a span of less than 10 days, both the registrars experienced a major hardware failure. The problem seems to be similar, it was a critical piece of equipment, and all the data was lost and had to be restored from backups.
Registrar 1 (smaller) took more than 2 days to become functional and even then the data was not properly restored. A lot of it had to be manually modified.
Registrar B had good systems in place and the data was restored quickly, with no loss of data.