During SCCC to CSRS upgrade, it's possible for setShardVersion to be called on a config server, causing it to cache a SCCC config server connection string. Later, if another SSV call runs with a CSRS connection string, the config server will attempt to call grid.forwardingCatalogManager()->scheduleReplaceCatalogManagerIfNeeded(), which will segfault because there is no catalog manager installed on config servers.