I've seen several times where the pyFTSIncrementalIndexer queue processor stops running.  Usually, if/when I've made an SR, we have treated the symptom, which includes a series of restarts, cache clears, etc.  Has anyone heard of a proactive fix...something that will prevent the actual issue from occurring in the first place?  Things have generally seemed to have gotten better, but it does still happen from time to time.  Just now, it is happening to me in an 8.5.4 environment.