SSL certificates are one essential key for proving
authenticity of an URL and also the encrypted data
transfer between client and server. But what happens
if an SSL certificate gets corrupted or misused?

Normally a certificate gets revoked and thus will be listed as insecure thereafter. But when this happens to at least 50% of your issued certificate, this can become a general issue and lead to massive problems not only with traffic encryption but also trust between the issuer and it’s customers.

Even root CAs might start to mistrust an entire branch which could lead to even more problems.

Although these certificates have been revoked, no actual problem for the web users should be visible as the revoked certificates are no longer active. However LetsEncrypt reserves the right to revoke the remaining certificates as they become replaced by new ones.

In general these certificates are only valid for 90 days if not extended automatically. So inactive certificates might become revoked by then and server admins might have to issue a new SSL certificate then.