While it’s true to say if you run something harder or faster it is more likely to break, and the speed you are running may strain or be indirectly responsible for the frequency of the fails. What you are seeing there has been reported before and as far as I know, not been diagnosed.
Search for “thread is dead” on the old forum and you will find a few references to it.
@Jon - although yours isn’t failing it is also faulty. Look at that centre column that reports the thread name, why is the RFM2Pi interfacer apparently publishing to MQTT? that should be the MQTT thread. Could you try restarting emonhub (sudo service emonhub restart) and recheck the log, see if it is correct from boot?