Job not been executed

[xxxifan]

I'm using it without any scheduler(so I don't use persist job either) with this configuration

Configuration.Builder builder = new Configuration.Builder(this)
                .loadFactor(5)
                .minConsumerCount(1)
                .maxConsumerCount(5);
        mJobManager = new JobManager(builder.build());

on our device (Android 5.1) without gcm services, some times(most of time) the job can't be executed, we can see like this

Logger.d("job " + job + "count " + mJobManager.count() + ", readyCount " + mJobManager.countReadyJobs() + ", threads " + mJobManager
                        .getActiveConsumerCount());

and output

count 8, readyCount 8, threads 2

and it just dont run. and some minutes later, it's started to run. I've read some code, I'm confused is there a BatchScheduler enabled? I don't specify any scheduler like the configuation did, and according to the code it should not have a default scheduler(If I'm not wrong), so what the problem is it?