The SCRJ was designed to be only run by KMail on start, however, since then there are a bunch of new Agents that use MailCommon::Kernel which will start SpecialMailCollectionRequestJob. This can create a race condition when all those agents and KMail will all try to create missing special collections.

Ideally, the first SCRJ would register a DBus service to "lock" other SCRJs that are started later so they would wait for the first one to finish before checking for and/or trying to create the special collections.