AppFabricTestBase starts an AppFabricServer that in turn starts a LocalRunRecordCorrectorService. That attempts to correct runs once immediately. However, at that time the MDS (app.meta) does not exist yet. That can make the getDataset() call take a long time and hence the run record corrector's transaction times out. This makes the AppFabricServer fail to start up, which fails the test case.
This is the cause for a good percentage of the current flaky tests.