In startStorageControls, we create a new instance of JournalFlusher and set it to the serviceContext. This is fine at startup time. But if startStorageControls is called during rollback, we will be destroying the existing instance of JournalFlusher which some preexisting callers of JournalFlusher::waitForJournalFlush may still have references to (via JournalFlusher::get). And so those callers could be accessing freed memory and would likely trash the memory.