It has been reported a lot ever since since MQTT was used to post direct to emoncms, even with the old Nodes module, eg see Phantom Duplicated MQTT Topics after reboot
According to that thread you need to recreate all your processing in the new input and use that instead of the old one, So I hope it doesn’t happen too frequently, that could get real annoying real fast!
EDIT - Maybe stopping the data (stop mosquitto or emonhub) delete the new input, flush redis and restart the data again might revive it. Or if you do need to swap to the new input, you may be able to use the input api’s to fetch the old processlist and then post it to the new input, I haven’t tried it but it might be possible.
EDIT2 - Beware flushing redis can have unwanted effects on some feeds.